VENOM-367: Add peers list to conference window

[naxuroqa]

• Add a small/compact peers overview in the conference window
• Add copyright notice to all files in ui folder
• Update potfiles

[codecov-io]

Codecov Report

Merging #367 into develop will decrease coverage by 0.09%. The diff coverage is 0%.

@@            Coverage Diff            @@
##           develop    #367     +/-   ##
=========================================
- Coverage     20.7%   20.6%   -0.1%     
=========================================
  Files           90      90             
  Lines         5235    5260     +25     
=========================================
  Hits          1084    1084             
- Misses        4151    4176     +25

Impacted Files	Coverage Δ
src/view/PeerEntry.vala	0% <0%> (ø)	:arrow_up:
src/view/ConferenceWindow.vala	0% <0%> (ø)	:arrow_up:

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