Replace Travis with GitHub actions and fix many typos (#1657)

* Create django.yml

* Fix working directory

* ..

* .

* ..

* a.

* ..

* .

* Fix typo

* Install hunspell

* maxfail

* Fix install

* .

* Reduce number of typos

* Even less typos

* Postgres debug

* Spelling fixes, yet again

* Postgres with PW

* Fix failing test

* New workflows

* Fix syntax error

* Install gettext

* Test aginst python 3.6 as well

* Clean up strategies

* Add badge, do not ignore migrations

* Use pip cache

src/pretix/locale/de/LC_MESSAGES/djangojs.po

@@ -606,8 +606,8 @@ msgstr "Dezember"
 #~ msgstr "Information zum Veranstalter"
 
 #~ msgid ""
-#~ "Addon 1\n"
-#~ "Addon 2"
+#~ "Add-on 1\n"
+#~ "Add-on 2"
 #~ msgstr ""
 #~ "Workshop 1\n"
 #~ "Workshop 2"