docs: API reference and getting-started guide for developers.pezkuwichain.io (#21)

* docs: generate the API reference for developers.pezkuwichain.io

Add TypeDoc (0.28.20) and `yarn docs`, which builds the reference for the
nine public API packages from src/ into build-docs/, with a landing page
and a getting-started guide whose examples were run against the live
network. The PR workflow builds it so a broken doc comment or config is
caught before merge.

docs/ held only a redirect to polkadot.js.org; it now holds the guide
sources. The README, packages/api/README.md and three CHANGELOG entries
linked to js.pezkuwichain.app, a domain that is not ours and is listed
for sale; they now point to developers.pezkuwichain.io, the Pezkuwi
Portal, or the upstream polkadot.js.org pages the entries came from.

* ci(docs): deploy the reference to developers.pezkuwichain.io

On every master push that changes the generated reference, build it with
`yarn docs` and publish it to the web host the same way pezkuwi-apps
publishes the portal: an approved production environment holds the deploy
key, the bundle is unpacked into releases/<sha>, and going live is one
rename of the current symlink. The switch is checked through nginx for the
public name (deploy sha, index, main.js, search index) and rolled back if
the new release is not served. workflow_dispatch with rollback_to makes an
earlier release live again.

Release-bot version bumps ([CI Skip]) and changes that cannot affect the
output do not ask for an approval.

README.md

@@ -10,7 +10,7 @@ This library provides a clean wrapper around all the methods exposed by a Pezkuw
 
 ## Documentation
 
-For complete documentation around the interfaces and their use, visit the [documentation portal](https://js.pezkuwichain.app/docs/api/).
+The API reference and a getting-started guide are at [developers.pezkuwichain.io](https://developers.pezkuwichain.io).
 
 ## Installation
 
@@ -48,7 +48,7 @@ console.log(`Connected to ${chain}`);
 
 ## Tutorials
 
-Looking for tutorials? Check out [examples](https://js.pezkuwichain.app/docs/api/examples/promise/) for guides on how to use the API to make queries and submit transactions.
+Looking for a walkthrough? [Getting started](https://developers.pezkuwichain.io/documents/Getting_started.html) connects, reads chain state, follows blocks and sends a transfer.
 
 ## Changelog
 
@@ -57,8 +57,8 @@ If you are an existing user, please track the [CHANGELOG](CHANGELOG.md) when cha
 ## Links
 
 - Website: https://pezkuwichain.io
-- Documentation: https://docs.pezkuwichain.io
-- API Docs: https://js.pezkuwichain.app
+- Developer docs: https://developers.pezkuwichain.io
+- Wiki: https://wiki.pezkuwichain.io
 - GitHub: https://github.com/pezkuwichain
 
 ## License