Add issue and pull request template (#1026)

* Add issue and pull request template

* Fix typo

.github/ISSUE_TEMPLATE.md

@@ -0,0 +1,14 @@
+# Impacted versions
+
+* Modoboa: X.X.x
+* installer used: Yes/No ?
+* Webserver: Nginx/Apache
+
+# Steps to reproduce
+
+# Current behavior
+
+# Expected behavior
+
+# Video/Screenshot link (optional)
+

.github/PULL_REQUEST_TEMPLATE.md

@@ -0,0 +1,5 @@
+Description of the issue/feature this PR addresses:
+
+Current behavior before PR:
+
+Desired behavior after PR is merged: