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>

.github/workflows/site-publish.yaml

@@ -0,0 +1,36 @@
+name: site-publish
+on:
+  push:
+    branches:
+      - main
+    paths:
+      - 'site/**'
+      - 'mkdocs/**'
+
+permissions:
+  contents: write
+
+jobs:
+  deploy_site:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Check out Git repository
+        uses: actions/checkout@v3
+
+      - name: Install Node.js, NPM and Yarn
+        uses: actions/setup-node@v3
+        with:
+          node-version: 20
+          cache: 'yarn'
+
+      - name: Yarn Install
+        run: yarn install --frozen-lockfile
+
+      - name: Yarn Build
+        run: yarn build
+
+      - uses: actions/setup-python@v4
+        with:
+          python-version: 3.x
+      - run: pip install mkdocs-macros-plugin mkdocs-redirects mkdocs-material
+      - run: cd mkdocs && mkdocs gh-deploy --force