docs: initialise new docs with docusaurus (#460)

* docs: initialise new docs with docusaurus

* chore: sign off
Signed-off-by: izzy <me@insrt.uk>

* chore: lock pnpm version in package.json

Signed-off-by: izzy <me@insrt.uk>

* ci: specify package json to load pnpm version from

Signed-off-by: izzy <me@insrt.uk>

* docs: update repo. lifecycle details

Signed-off-by: izzy <me@insrt.uk>

* docs: add external links to for-web, for-android
chore: add default.nix to docs

* docs: correct headings in contrib

* ci: use cache dependency path

* fix: docusaurus configuration

---------

Signed-off-by: izzy <me@insrt.uk>

docs/sidebars.ts

@@ -0,0 +1,49 @@
+import type { SidebarsConfig } from '@docusaurus/plugin-content-docs';
+
+const sidebars: SidebarsConfig = {
+  docsSidebar: [
+    'index',
+    'help',
+    'faq',
+    {
+      type: 'category',
+      label: "Developers",
+      link: {
+        type: "generated-index",
+        description: "Building with Stoat"
+      },
+      items: [
+        {
+          type: 'autogenerated',
+          dirName: 'developers',
+        }
+      ]
+    },
+    {
+      type: 'category',
+      label: "Developing Stoat",
+      link: {
+        type: "generated-index",
+        description: "Building Stoat"
+      },
+      items: [
+        {
+          type: 'autogenerated',
+          dirName: 'developing',
+        },
+        {
+          type: 'link',
+          label: "for Web",
+          href: "https://stoatchat.github.io/for-web"
+        },
+        {
+          type: 'link',
+          label: "for Android",
+          href: "https://stoatchat.github.io/for-android"
+        }
+      ]
+    }
+  ],
+};
+
+export default sidebars;