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>

site/docs/stylesheets/extra.css

@@ -0,0 +1,163 @@
+/* Font style definitions */
+
+@font-face {
+    font-family: 'Recursive';
+    font-style: oblique 0deg 15deg;
+    font-weight: 300 1000;
+    src: url('../assets/fonts/Recursive_VF_1.084.woff2') format('woff2');
+    font-feature-settings: "ss12";
+}
+
+@font-face {
+    font-family: 'Inter';
+    font-weight: 100 900;
+    font-display: swap;
+    font-style: normal;
+    src: url('../assets/fonts/Inter.var.woff2') format('woff2');
+    font-feature-settings: "ss03";
+}
+
+@font-face {
+    font-family: 'Inter';
+    font-weight: 100 900;
+    font-display: swap;
+    font-style: italic;
+    src: url('../assets/fonts/Inter-Italic.var.woff2') format('woff2');
+    font-feature-settings: "ss03";
+}
+  
+:root {
+    --md-code-font: "Recursive", monospace;
+    --md-text-font: "Inter", "Helvetica", "Arial", sans-serif;
+    --wr-blue-primary: #0891B2;
+    --wr-orange-primary: #C96509;
+}
+
+[data-md-color-scheme="webrecorder"] {
+    --md-primary-fg-color: #4D7C0F;
+    --md-primary-fg-color--light: #0782A1;
+    --md-primary-fg-color--dark: #066B84;
+    --md-typeset-color: black;
+    --md-accent-fg-color: #0782A1;
+    --md-typeset-a-color: #066B84;
+    --md-code-bg-color: #F9FAFB;
+  }
+
+/* Nav changes */
+
+.md-header__title {
+    font-family: var(--md-code-font);
+    font-variation-settings: "MONO" 0.51;
+}
+
+.md-header__title--active {
+    font-family: var(--md-text-font);
+    font-weight: 600;
+}
+
+/* Custom menu item hover */
+
+.md-tabs__link {
+    font-family: var(--md-code-font);
+    font-weight: 400;
+    opacity: .9;
+    transition: .4s cubic-bezier(.1,.7,.1,1),opacity .25s
+}
+
+.md-tabs__link:hover {
+    font-weight: 600;
+}
+
+/* Custom body typography rules */
+
+.md-typeset a {
+    text-decoration: underline;
+}
+
+.headerlink {
+    text-decoration: none!important;
+}
+
+code, pre, kbd {
+    font-variation-settings: "MONO" 1;
+    font-feature-settings: "ss01", "ss02", "ss08";
+}
+
+code {
+    border-width: 1px;
+    border-color: #D1D5DB;
+    border-style: solid;
+}
+
+.md-typeset h1, h2, h3, h4, h5 {
+    color: black;
+}
+
+.md-typeset h1, h2, h3 {
+    font-weight: 650 !important;
+    font-variation-settings: "OPSZ" 35;
+}
+
+.wr-container {
+    border-radius: 0.25rem;
+    border-width: 1px;
+    border-color: #D1D5DB;
+    border-style: solid;
+}
+
+/* Custom badge classes, applies custom overrides to inline-code blocks */
+
+.badge-blue {
+    background-color: var(--wr-blue-primary) !important;
+    border-color: var(--wr-blue-primary) !important;
+    color: white !important;
+    font-family: var(--md-text-font);
+    font-weight: 600;
+}
+
+.badge-orange {
+    background-color: var(--wr-orange-primary) !important;
+    border-color: var(--wr-orange-primary) !important;
+    color: white !important;
+    font-family: var(--md-text-font);
+    font-weight: 600;
+}
+
+
+/* Status Styling */
+
+.status-success {
+    font-family: var(--md-code-font);
+    font-weight: 500;
+    white-space: nowrap;
+    & svg {
+        color: hsl(142.1 76.2% 36.3%);
+    }
+}
+
+.status-warning {
+    font-family: var(--md-code-font);
+    font-weight: 500;
+    white-space: nowrap;
+    & svg {
+        color: hsl(32.1 94.6% 43.7%);
+    }
+}
+
+.status-danger {
+    font-family: var(--md-code-font);
+    font-weight: 500;
+    white-space: nowrap;
+    & svg {
+        color: hsl(0 72.2% 50.6%);
+    }
+}
+
+.status-waiting {
+    font-family: var(--md-code-font);
+    font-weight: 500;
+    white-space: nowrap;
+    & svg {
+        color: hsl(271.5 81.3% 55.9%);
+    }
+}