Do not include non-package files in wheel

See merge request AlekSIS/official/AlekSIS-App-Chronos!232

Resolve "Show notification if no timetable exists in one category"

Closes #86

See merge request AlekSIS/official/AlekSIS-App-Chronos!231

Resolve "Ignore subject color in timetable if fg == bg"

Closes #160

See merge request AlekSIS/official/AlekSIS-App-Chronos!229

Prepare release 2.1

See merge request !228

Translations update from Weblate

See merge request !225

Resolve "Automatic plan update fails because of missing version object"

Closes #159

See merge request !223

Currently translated at 100.0% (135 of 135 strings)

Translation: AlekSIS/AlekSIS-App-Chronos
Translate-URL: https://translate.edugit.org/projects/aleksis/aleksis-app-chronos/de/

Update translation files

See merge request !226

Drop poetry.lock

See merge request !224

Fix readme reference

See merge request !222

Resolve "Names of subjects should not have to be unique"

Closes #158

See merge request !221

[Fixtures] Fix number and period of validity ranges

See merge request !220

Remove admin user from test data

See merge request !219

Add trademark hint to readme

See merge request !218

Resolve "Allow editing of subject field on Group model in frontend"

Closes #156

See merge request !215

Resolve "Announcements are not shown on substitutions printout"

Closes #157

See merge request !216

Update dev dependencies and reformat

See merge request !217