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/package.json

@@ -0,0 +1,50 @@
+{
+  "name": "docs",
+  "version": "0.0.0",
+  "private": true,
+  "scripts": {
+    "docusaurus": "docusaurus",
+    "start": "docusaurus start",
+    "build": "docusaurus build",
+    "swizzle": "docusaurus swizzle",
+    "deploy": "docusaurus deploy",
+    "clear": "docusaurus clear",
+    "serve": "docusaurus serve",
+    "write-translations": "docusaurus write-translations",
+    "write-heading-ids": "docusaurus write-heading-ids",
+    "typecheck": "tsc"
+  },
+  "dependencies": {
+    "@docusaurus/core": "3.9.2",
+    "@docusaurus/plugin-client-redirects": "^3.9.2",
+    "@docusaurus/preset-classic": "3.9.2",
+    "@mdx-js/react": "^3.0.0",
+    "@scalar/docusaurus": "^0.7.21",
+    "clsx": "^2.0.0",
+    "prism-react-renderer": "^2.3.0",
+    "react": "^19.0.0",
+    "react-dom": "^19.0.0"
+  },
+  "devDependencies": {
+    "@docusaurus/module-type-aliases": "3.9.2",
+    "@docusaurus/tsconfig": "3.9.2",
+    "@docusaurus/types": "3.9.2",
+    "typescript": "~5.6.2"
+  },
+  "browserslist": {
+    "production": [
+      ">0.5%",
+      "not dead",
+      "not op_mini all"
+    ],
+    "development": [
+      "last 3 chrome version",
+      "last 3 firefox version",
+      "last 5 safari version"
+    ]
+  },
+  "engines": {
+    "node": ">=20.0"
+  },
+  "packageManager": "pnpm@10.22.0+sha512.bf049efe995b28f527fd2b41ae0474ce29186f7edcb3bf545087bd61fbbebb2bf75362d1307fda09c2d288e1e499787ac12d4fcb617a974718a6051f2eee741c"
+}