feat(Reaction): add styles for dark and hoc Teams theme

[mnajdova]

This PR adds updates on the Reactions component in dark and hoc Teams themes, and adds the new focus indicator.
Light theme:

Dark theme:

HOC:

The pictures are taken from the Prototypes for the ChatMessages.

[codecov]

Codecov Report

Merging #1152 into master will decrease coverage by 0.02%.
The diff coverage is 57.14%.

@@            Coverage Diff             @@
##           master    #1152      +/-   ##
==========================================
- Coverage   82.48%   82.46%   -0.03%     
==========================================
  Files         733      735       +2     
  Lines        8717     8724       +7     
  Branches     1232     1235       +3     
==========================================
+ Hits         7190     7194       +4     
- Misses       1511     1514       +3     
  Partials       16       16

Impacted Files	Coverage Δ
...mes/teams/components/Reaction/reactionVariables.ts	100% <ø> (ø)	⬆️
...themes/teams/components/Reaction/reactionStyles.ts	33.33% <0%> (-11.12%)	⬇️
...eams-dark/components/Reaction/reactionVariables.ts	100% <100%> (ø)
.../react/src/themes/teams-dark/componentVariables.ts	100% <100%> (ø)	⬆️
...-contrast/components/Reaction/reactionVariables.ts	100% <100%> (ø)
...c/themes/teams-high-contrast/componentVariables.ts	100% <100%> (ø)	⬆️

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