* Extensions docs: add npm/bundler installation guide and up versions numbers for links
* Revert extensions._index.md table change
* Update docs.md extension installation and integration instruction
* Move extension installation and enabling to new sections in docs.md
* Update extension installation guidelines
* Update idiomorph installation guidelines
* Minor consistency edits
* Make the need for hx-ext clearer
* Fix typos and note for community repos not hosted outside this repo