doc: updated PR template, refer to Wiki on how to make new release

Author: edkerk

.github/pull_request_template.md

@@ -1,14 +1,14 @@
 ### Main improvements in this PR:
 <!-- Pointwise mention what changes were made in what function. Examples: 
-- Fixes:
+- fix:
   - `functionName` failed to do action X
-- Documentation:
-  - Updated all documentation 
-- Features:
-  - Introduced option to do function Y (issue #12345) -->
+- documentation:
+  - updated all documentation 
+- features:
+  - introduced option to do function Y (solves #12345) -->
 
 #### Instructions on merging this PR:
 <!-- Chose ONE of the following two options
 and replace [ ] with [X] to check the box.-->
 - [ ] This PR has `develop` as target branch, and will be resolved with a *squash-merge*.
-- [ ] This PR has `main` as target branch, and will be resolved with a *merge commit*.
+- [ ] This PR has `main` as target branch, and will be resolved as descriped [here](https://github.com/SysBioChalmers/RAVEN/wiki/Development-policy#make-a-new-release).