Suppression list

sparkpost_civicrm_check: correct version check function (critical for 5.0)

add configurable custom callback URL.

typos

Adding documentation on bounce processing.

Updating documentation link

ensure bullets render correctly in documentation home page

see https://github.com/civicrm/civicrm-dev-docs/commit/e1b32fc4fd7c2c61ae25a776fde29d54cf7af114

Spelling fix.

typo fix

"as" -> "are"

Docs cleanup

https://docs.civicrm.org/dev/en/master/best-practices/documentation-style-guide/#describing-the-civicrm-user-interface
https://docs.civicrm.org/dev/en/master/best-practices/documentation-style-guide/#urls

(lists must be separated from paragraphs)

(Sublists need to be indented by 4 spaces)
https://docs.civicrm.org/dev/en/master/markdownrules/#nested-lists

Using one and only one H1 element per page

This puts a link to GitHub within the site header and also enables a
pencil icon at the top right of every page for people to suggest edits