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>

.github/workflows/docs-test.yml

@@ -0,0 +1,29 @@
+name: Documentation (test)
+
+on:
+  pull_request:
+
+jobs:
+  test-deploy:
+    name: Test deployment
+    runs-on: ubuntu-latest
+    defaults:
+      run:
+        working-directory: ./docs
+    steps:
+      - uses: actions/checkout@v4
+        with:
+          fetch-depth: 0
+      - uses: pnpm/action-setup@v4
+        with:
+          package_json_file: ./docs/package.json
+      - uses: actions/setup-node@v4
+        with:
+          node-version: lts/*
+          cache: pnpm
+          cache-dependency-path: ./docs/pnpm-lock.yaml
+
+      - name: Install dependencies
+        run: pnpm install
+      - name: Test build website
+        run: pnpm run build