Update "Building the Docs" info

[MoltonMontro]

Making a note that I should update this info. It's still relatively straightforward, but there's an official Esbonio extension now. Live Preview is now part of this extension, and has been removed from the reStructedText extension. People migrating to the extension may need to manually uninstall Esbonio before reinstalling the extension.

• https://docs.lextudio.com/restructuredtext/articles/preview
• https://docs.esbon.io/en/latest/lsp/howto/migrate-to-v1.html#lsp-v1-migration

[SDGNelson]

Exciting quality of life improvements for editing! Thanks for noting to update the building tips.

[MoltonMontro]

Added new building info as part of the RTD Addons stuff / deprecation of Sphinx content injection.