Better docs

Signed-off-by: Thomas Citharel <tcit@tcit.fr>

Nicer docs

No 3rd stage

Add mix.deps get before docs

Add :ex_doc on test env so that it runs into CI

.gitlab/issue_templates/Bug.md

@@ -0,0 +1,29 @@
+#### Description
+
+[Description of the issue]
+
+#### Steps to Reproduce
+
+1. [First Step]
+2. [Second Step]
+3. [and so on...]
+
+#### Expected behaviour:
+
+[What you expect to happen]
+
+#### Actual behaviour:
+
+[What actually happens]
+
+#### Reproduces how often:
+
+[What percentage of the time does it reproduce?]
+
+#### Versions
+
+[What Mobilizon instance you're using, and the versions of each relevant app or component, including your OS and browser.]
+
+#### Additional Information
+
+[Any additional information, configuration or data that might be necessary to reproduce the issue.]