Document local deployment of the search page

The existing README.md file was just a template created in the very beginning of the GitHub RSpec project. It is severely outdated. I've recovered the proper deployment sequence.

frontend/README.adoc

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+
+= Search page for the rule repository
+
+This is a single-page React application that indexes the rule repository and
+allows you to run flexible search through all of the rules and rule drafts,
+and render the rule specifications in HTML.
+The render is not guaranteed to match the rule rendering in the products,
+but it is a good proxy.
+
+== Local deployment
+
+Make sure you have NodeJs and `npm` available. Tested with NPM v10.2.3 and NodeJS v18.19.0.
+
+Install dependencies
+
+[source,shell]
+----
+npm install
+----
+
+If you have some non-js dependencies missing, this might fail.
+Possibly missing non-js dependencies include OpenSSL, libuv, libssh2, KRB5.
+
+Once you succeed in installing the dependencies you are ready to predeploy.
+
+[source,shell]
+----
+npm run predeploy
+----
+
+This command builds the database of the rule specifications.
+
+NOTE: If the script fails to clone or fetch due to an SSL certificate failure
+      and your network uses a custom CA certificate you might need to make sure it is installed
+      in the accessible place.
+      As a workaround you can https://github.com/nodegit/nodegit/issues/1742[disable the certificate check].
+
+NOTE: In the predeploy step (specifically the `prepare-rules` part of it) the script fetches all the open PRs locally.
+      You might want to set `GITHUB_TOKEN` to your personal GitHub token
+      to avoid GitHub throttling your requests during the predeploy stage.
+
+
+Now you can run it locally:
+
+[source,shell]
+----
+npm start
+----
+
+This should open https://localhost:3000/rspec in your default browser with the rule search page.