fix(menu): highlight when active anchors

[Tibing]

Please read and mark the following check list before creating a pull request:

• I read and followed the CONTRIBUTING.md guide.
• I read and followed the New Feature Checklist guide.

Short description of what this resolves:

Closes #875

[Tibing]

Let's keep it opened until #1041 will be resolved. I have some ideas on how to completely solve this challenge but we can't be sure that all the things work fine without tests.

[codecov]

Codecov Report

Merging #1034 into master will decrease coverage by <.01%.
The diff coverage is 83.33%.

@@            Coverage Diff             @@
##           master    #1034      +/-   ##
==========================================
- Coverage   80.68%   80.68%   -0.01%     
==========================================
  Files         232      232              
  Lines        7032     7041       +9     
  Branches      593      595       +2     
==========================================
+ Hits         5674     5681       +7     
- Misses       1184     1185       +1     
- Partials      174      175       +1

Impacted Files	Coverage Δ
...work/theme/components/menu/url-matching-helpers.ts	100% <100%> (ø)	⬆️
...rc/framework/theme/components/menu/menu.service.ts	65.24% <71.42%> (-0.45%)	⬇️

[Tibing]

Let's write regression tests for NbMenuComponent. Which verify that fragment selection works properly.

[nnixaa]

@yggg tests are failing :(

[yggg]

I've fixed unit tests but looks like something is wrong with browser stack tunnel.