📝 Add dev docs to README, improve style guide adherence

This commit makes several mostly cosmetic changes to the AsciiDoc source
material for the Mindshare Committee documentation index page:

* Adhere to one-sentence-per-line convention
* Add header anchors to all anchors (easier to change the headers later
  without breaking existing links)
* Update "FCAIC" to "FCA" and link to Council role page where applicable
* Minor styling and cosmetic changes

Additionally, the README was updated to better explain this repository's
purpose and how to build the documentation site in a local environment.

Signed-off-by: Justin W. Flory (he/him) <jwf@redhat.com>