mgr/dashboard: Add a linter for closing tags in Angular templates
An issue with an unclosed tag has been found and fixed. The tool we currently use, `html-linter`, was not capable of finding that issue and the documentation refers to a configuration file which does not seem to support finding such issues. There's a tool that did find it, though, called `html-hint`. `html-hint` is more vidid (when compared with html-linter by weekly downloads on npm) but seems to have a slightly different focus. I therefore recommend to integrate `html-hint` in addition to `html-linter` in `run-frontend-unit-tests.sh`. The integration in `run-frontend-uni-tests.sh` will ensure that such errors can not sneak into our code anymore.
user@home ~/src/ceph-4/src/pybind/mgr/dashboard/frontend (wip-pna-fix-tag*) $ npx htmlhint -r tag-pair src/app /home/user/src/ceph-4/src/pybind/mgr/dashboard/frontend/src/app/app.component.html L9 | ^ Tag must be paired, missing: [ </block-ui></block-ui> ], open tag match failed [ <block-ui> ] on line 8. (tag-pair) Scanned 121 files, found 1 errors in 1 files (146 ms) user@home ~/src/ceph-4/src/pybind/mgr/dashboard/frontend (wip-pna-fix-tag*) $ ..