Heroku integration

[bogdal]

This PR adds Heroku integration.

Screenshot

Pull Request Checklist

1. All visible strings are translated with proper context.
2. All data-formatting is locale-aware (dates, numbers, and so on).
3. Translated strings are extracted to .pot file.
4. Number of API calls is optimized.
5. The changes are tested.
6. Type definitions are up to date.
7. Changes are mentioned in the changelog.

[codecov]

Codecov Report

Merging #175 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #175   +/-   ##
=======================================
  Coverage   73.33%   73.33%           
=======================================
  Files         538      538           
  Lines        5445     5445           
  Branches      940      940           
=======================================
  Hits         3993     3993           
  Misses       1289     1289           
  Partials      163      163

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