Tracking issue: advanced search features

[grunweg]

Let's collect all ideas for "more advanced search" here:

• by author: author:grunweg etc. - implemented with a small hack #...

• by assignee: assignee:grunweg etc. - unimplemented; would be easy to add

• labels, with the t-algebra$ tweak - implemented with a small hack

• Disable searching in the description (feat: synthetic test fixtures and CI #79)? I guess that is not necessary; providing more localised ways of searching certain fields seems more useful. The only one remaining could be the PR title.

• search for a list of authors (compute areas at max capacity and show in a table #72): authors:grunweg,jcommelin finds all PRs by grunweg or jcommelin

• logical operators: OR and NOT (fix: missed an occurrence of all-open-PRs-2.json #84)