Update application store assets

[bmarty]

Content

Add a new image and update title, short description and long description of the application.

New content will be used once the PR is merged for the next release on F-Droid.
For GPlay, I'll update the content on the PlayStore once the PR has been approved and merged.

• content updated on the PlayStore

Motivation and context

Screenshots / GIFs

Tests

• NA

Tested devices

• NA

Checklist

• Changes have been tested on an Android device or Android emulator with API 23
• UI change has been tested on both light and dark themes
• Accessibility has been taken into account. See https://github.com/element-hq/element-x-android/blob/develop/CONTRIBUTING.md#accessibility
• Pull request is based on the develop branch
• Pull request title will be used in the release note, it clearly define what will change for the user
• Pull request includes screenshots or videos if containing UI changes
• Pull request includes a sign off
• You've made a self review of your PR

[github-actions]

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[sonarcloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarCloud

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 82.61%. Comparing base (78d13fc) to head (56b0553).
Report is 12 commits behind head on develop.

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #3441      +/-   ##
===========================================
- Coverage    82.61%   82.61%   -0.01%     
===========================================
  Files         1699     1699              
  Lines        39989    39989              
  Branches      4866     4866              
===========================================
- Hits         33036    33035       -1     
  Misses        5233     5233              
- Partials      1720     1721       +1     

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[jmartinesp]

LGTM!