Documentation: Update docs tool to omit private, experimental, unstable APIs

[aduth]

Closes #15148

This pull request seeks to update the docs tool to omit selectors and actions which are either named as unstable or experimental, or which include a @private JSDoc tag.

• https://github.com/WordPress/gutenberg/blob/master/docs/contributors/coding-guidelines.md#experimental-and-unstable-apis
• http://usejsdoc.org/tags-private.html

Implementation notes:

There is certainly some overlap / potential for inconsistency between the documentation output by this tool, and that of @wordpress/docgen. These should probably be reconciled, but it seemed a larger effort than the immediate goal of excluding APIs not intended to be documented.

Testing instructions:

Verify there are no unstable, experimental, or private APIs documented.

Verify there are no local changes after running npm run docs:build in this branch.

[gziolo]

Can we make it case insensitive? I'd like it to cover component names as well:

__UnstableComponent or __ExperimentalComponent.

[aduth]

Can we make it case insensitive? I'd like it to cover component names as well:

__UnstableComponent or __ExperimentalComponent.

AFAIK (and what I'd recommend), it's still capitalized as __experimentalComponent.

Example:

gutenberg/packages/data/src/index.js

Line 16 in da09d36

export { default as __experimentalAsyncModeProvider } from './components/async-mode-provider';

[gziolo]

Okay, let's follow this pattern 👍

[aduth]

There is certainly some overlap / potential for inconsistency between the documentation output by this tool, and that of @wordpress/docgen. These should probably be reconciled, but it seemed a larger effort than the immediate goal of excluding APIs not intended to be documented.

#15200 is a step toward this.

[gziolo]

Let's move forward with it and focus our efforts on moving selectors and actions under control of docgen 👍