chore(docs): [DREL-220] Bump Docusaurus and TypeDoc (#2920)

## Summary

Old docusaurus and its typescript version are blocking the upgrades of
network team -> Killed the ailing docusaurus 2.x docs and re-created new
docs with latest docusaurus 3.6.3.

Docusaurus installation is kept as vanilla as possible.

## Changes

- Docusaurus 2.x has been retired.
- Custom scripts used in previous version to customize styles on API
pages have been retired.
 
## Limitations and future improvements

- Inject typedoc generated sidebar to docusaurus sidebar ts.
- "Important classes" highlighed (i.e. @category Important in TypeDoc)?
- Fixing Non-trailing slash redirects should now be easier in docusaurs
3.x

Author: yaruno

docs/.gitignore

@@ -7,7 +7,6 @@
 # Generated files
 .docusaurus
 .cache-loader
-/docs/usage/sdk/api
 
 # Misc
 .DS_Store
@@ -20,3 +19,6 @@ npm-debug.log*
 yarn-debug.log*
 yarn-error.log*
 /.vscode
+
+# Autogenerated API documentation
+/docs/usage/sdk/api

docs/.nvmrc

@@ -10,5 +10,9 @@ For ease of use, small changes can be suggested by editing the markdown file on
 ### Run it locally
 Simply, `npm ci` & `npm start`
 
-## Streamr core devs
-Deployments are automatically made after every commit to `main`, therefore editing markdown files directly on `main` will be reflected in production within a minute or two.
+### Create & serve production build locally
+Simply, `npm ci` & `npm run build` & `npm run serve`
+
+### Clean & clear build folder
+Simply, `npm run clear`
+