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/control/templates/pretixcontrol/orders/cancel.html

@@ -50,7 +50,7 @@
             <div class="alert alert-info" data-display-dependency="#id_refund_as_giftcard">
                 {% blocktrans trimmed %}
                     Since you are refunding your customers orders to gift cards, you should explain to them how to
-                    access their giftcards. The easiest way to do this, is to include an explanation and a link to
+                    access their gift cards. The easiest way to do this, is to include an explanation and a link to
                     their order using the here provided email functionality.
                 {% endblocktrans %}
             </div>