MKDocs conversion (#278)

Closes #252, Closes #250

## Changes
- ReplayWeb.page uses MKDocs for documentation now!
- Requires both
[`mkdocs-macros`](https://mkdocs-macros-plugin.readthedocs.io/en/latest/)
and [`mkdocs-redirects`]
(https://github.com/mkdocs/mkdocs-redirects) plugins to be installed
- Redirects existing docs pages to their new locations under either
`/embedding` or `/user-guide`
- Unused images have been removed
- Adds new ReplayWeb.page branding!

All pages have received copy edits. All references to future (or
previously) planned features have been removed. More major content
changes of note are as follows:

### Supported Locations
- Made into a page, no longer a table. Locations are either supported or
not listed.

### Offline Use 
- Removes browser cache section, adds improved PWA install and uninstall
instructions.
- Removes navigation instructions to GitHub's releases section in favour
of a link

### Supported Formats
- Moved to the User Guide homepage
- Updated the format support

### Exploring Archives
- Example links for showcasing features have been moved to their
respective feature documentation section on this page

### Remove Usage, Examples, and Troubleshooting Pages
- Usage content is covered in the user guide index
- Troubleshooting content has been added to a question section on the
getting started page about WARC vs WACZ.
- Examples are now Featured Projects on the docs homepage!

### Build Process
- Removes Jekyll & related site assets.
- Adds new GitHub action for publishing
- Adds a python macro to dynamically load the replayweb.page version from package.json
- Relocates replayweb.page site content under /site (including docs)
- Some assets (favicon, logo) and sw.js/ui.js automatically copied into /site

---------
Co-authored-by: Ilya Kreymer <ikreymer@gmail.com>

mkdocs/main.py

@@ -0,0 +1,18 @@
+import json
+
+def define_env(env):
+    """
+    This is the hook for the functions (new form)
+    """
+    version = "LATEST"
+    try:
+        with open("../package.json") as fh:
+            version = json.loads(fh.read())["version"]
+    except:
+        pass
+
+    @env.macro
+    def rwp_version():
+        "get the version"
+        return version
+

mkdocs/mkdocs.yml

@@ -0,0 +1,110 @@
+site_name: ReplayWeb.page Docs
+docs_dir: ../site/
+watch:
+  - ../site/
+site_dir: _genhtml/
+repo_url: https://github.com/webrecorder/replayweb.page
+repo_name: ReplayWeb.page
+edit_uri: edit/main/site/docs/
+extra_css:
+    - docs/stylesheets/extra.css
+extra_javascript:
+    - docs/js/sw.js
+theme:
+  name: material
+  custom_dir: ../site/docs/overrides
+  features:
+    - navigation.sections
+    - navigation.tabs
+    - navigation.tabs.sticky
+    - navigation.instant
+    - navigation.tracking
+    - navigation.indexes
+    - navigation.footer
+    - content.code.copy
+    - content.action.edit
+    - content.tooltips
+    - search.suggest
+  palette:
+    scheme: webrecorder
+  logo: docs/assets/brand/replaywebpage-icon-white.svg
+  favicon: docs/assets/brand/favicon.svg
+
+  icon:
+    admonition:
+      note: bootstrap/pencil-fill
+      abstract: bootstrap/file-earmark-text-fill
+      info: bootstrap/info-circle-fill
+      tip: bootstrap/exclamation-circle-fill
+      success: bootstrap/check-circle-fill
+      question: bootstrap/question-circle-fill
+      warning: bootstrap/exclamation-triangle-fill
+      failure: bootstrap/x-octagon-fill
+      danger: bootstrap/exclamation-diamond-fill
+      bug: bootstrap/bug-fill
+      example: bootstrap/mortarboard-fill
+      quote: bootstrap/quote
+
+    repo: bootstrap/github
+    edit: bootstrap/pencil
+    view: bootstrap/eye
+
+nav:
+  - docs/index.md
+  - Embedding:
+    - docs/embedding/index.md
+    - docs/embedding/cors-settings.md
+  - User Guide:
+    - docs/user-guide/index.md
+    - docs/user-guide/loading.md
+    - docs/user-guide/locations.md
+    - docs/user-guide/exploring.md
+    - docs/user-guide/sharing.md
+    - docs/user-guide/offline-use.md
+
+markdown_extensions:
+  - toc: 
+      toc_depth: 3
+      permalink: true
+  - pymdownx.highlight:
+      anchor_linenums: true
+  - pymdownx.emoji:
+      emoji_index: !!python/name:material.extensions.emoji.twemoji
+      emoji_generator: !!python/name:material.extensions.emoji.to_svg
+      options:
+        custom_icons:
+          - ../site/docs/overrides/.icons
+  - admonition
+  - pymdownx.inlinehilite
+  - pymdownx.details
+  - pymdownx.superfences
+  - pymdownx.keys
+  - def_list
+  - attr_list
+
+extra:
+  generator: false
+  social:
+    - icon: bootstrap/globe
+      link: https://webrecorder.net
+    - icon: bootstrap/chat-left-text-fill
+      link: https://forum.webrecorder.net/
+    - icon: bootstrap/mastodon
+      link: https://digipres.club/@webrecorder
+    - icon: bootstrap/youtube
+      link: https://www.youtube.com/@webrecorder
+copyright: "Creative Commons Attribution 4.0 International (CC BY 4.0)"
+
+plugins:
+  - macros
+  - search
+  - redirects:
+      redirect_maps:
+        'docs/cors-settings.md': 'docs/embedding/cors-settings.md'
+        'docs/usage.md': 'docs/user-guide/index.md'
+        'docs/loading_online.md': docs/user-guide/loading.md
+        'docs/loading_offline.md': docs/user-guide/offline-use.md
+        'docs/exploring.md': 'docs/user-guide/exploring.md'
+        'docs/sharing.md': 'docs/user-guide/sharing.md'
+        'docs/locations.md': 'docs/user-guide/locations.md'
+        'docs/formats.md': 'docs/user-guide/index.md#supported-formats'