chore: add files to .gitignore

[charles-zablit]

This PR adds a few files to the .gitignore.

• .DS_Store are automatically generated files on MacOS that manages thumbnails, they shouldn't be added to the repository. Please let me know what you think of this change, as some people have it in their global .gitignore.
• out is the target folder when building artifacts with IntelliJ.

Please let me know if I can edit anything on this PR.

[codecov]

Codecov Report

Merging #450 (7855787) into master (171e240) will increase coverage by 0.02%.
The diff coverage is n/a.

Additional details and impacted files

@@             Coverage Diff              @@
##             master     #450      +/-   ##
============================================
+ Coverage     23.11%   23.14%   +0.02%     
  Complexity      305      305              
============================================
  Files            69       69              
  Lines          5810     5812       +2     
  Branches        789      790       +1     
============================================
+ Hits           1343     1345       +2     
  Misses         4236     4236              
  Partials        231      231              

Impacted Files	Coverage Δ
...c/main/java/org/jitsi/jigasi/stats/Statistics.java	42.38% <0.00%> (-1.33%)	⬇️
...jigasi/transcription/VoskTranscriptionService.java	0.00% <0.00%> (ø)
src/main/java/org/jitsi/jigasi/JvbConference.java	45.08% <0.00%> (+0.14%)	⬆️
.../jitsi/jigasi/sounds/SoundNotificationManager.java	30.45% <0.00%> (+0.82%)	⬆️
...in/java/org/jitsi/jigasi/sounds/PlaybackQueue.java	56.14% <0.00%> (+1.75%)	⬆️

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