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/.gitignore

@@ -0,0 +1,20 @@
+# Dependencies
+/node_modules
+
+# Production
+/build
+
+# Generated files
+.docusaurus
+.cache-loader
+
+# Misc
+.DS_Store
+.env.local
+.env.development.local
+.env.test.local
+.env.production.local
+
+npm-debug.log*
+yarn-debug.log*
+yarn-error.log*