add popover attributes

[dkirchhof]

Adds popover, popoverTarget and popoverTargetAction to JsxDOM.domProps

[dkirchhof]

🤔 Do I have to write the Completion.res.txt stuff manually or is there a script to generate it?

[nojaf]

Try running make test inside tests/analysis_tests. (Or something along those lines, on my phone now)

[dkirchhof]

Unfortunatelly I don't get the toolchain running. Probably my python version is too new.
I didn't want to put much effort into this small change. Feel free to close this PR or maybe someone else could fix the tests.