update TB 11.5 screenshots

In this merge request:

1. I have updated all existing screenshots from the latest TB 11.5 stable
2. Removed screenshots of TB Alpha
3. Fixed image paths to be relative (and in markdown so that they show up properly)
4. close #123 (closed)

requested review from @emmapeel

assigned to @championquizzer

mentioned in commit 0be0c5dc

merged