5.10.0: Use "aggregating functions" consistently (#686) (#689)

Plus some minor editorial corrections.

5.8.0: Add missing docs for COLLECT (#605) (#606)

These parts existed for EXISTS and COUNT, but not for COLLECT.

---------
Cherry-picked from #605

Co-authored-by: Louise Söderström <[email protected]>

5.7.0: Fix misaligned entries in the TOC (#554) (#556)

It's likely that we won't need an appendix soon, especially given that
right now there is only 1 entry in it, but this PR fixes the
misalignment in the TOC for that chapter.

5.6.0: Update readme (#498)

The main purpose of this PR is to test and investigate build triggers