doc: add NEWS entries for recent doc and install changes
doc: fix favicon black background on alpha-naive viewers
doc: add developer guide describing CI usage
Rename COPYING.GPLv2 to COPYING
gh: record Scorecard in security-insights tools
gh: add OpenSSF Best Practices badge to README and security-insights
build(deps): bump actions/checkout from 6 to 7
build(deps): bump github/codeql-action from 3 to 4.37.3