Pull request template update

New version of the PR template.

Ideal PR should contain:

- detailed description of changes
- how it was tested
- dependencies
- PR type (one of)

.github/pull_request_template.md

@@ -1,39 +1,11 @@
-Notes:
-- Pull requests will not be accepted until the submitter has agreed to the [contributer agreement](https://github.com/ARMmbed/mbed-os/blob/master/CONTRIBUTING.md).
-- This is just a template, so feel free to use/remove the unnecessary things
+# Description
 
-## Description
+> Detailed changes summary | testing | dependencies
+> Good example: https://os.mbed.com/docs/latest/reference/guidelines.html#workflow (Pull request template)
 
-A few sentences describing the overall goals of the pull request's commits.
+# Pull request type
 
-## Status
-
-**READY/IN DEVELOPMENT/HOLD**
-
-## Migrations
-
-If this PR changes any APIs or behaviors, give a short description of what *API users* should do when this PR is merged.
-
-YES | NO
-
-## Related PRs
-
-List related PRs against other branches:
-
-branch | PR
------- | ------
-other_pr_production | [link]()
-other_pr_master | [link]()
-
-## Todos
-
-- [ ] Tests
-- [ ] Documentation
-
-## Deploy notes
-
-Notes regarding the deployment of this PR. These should note any required changes in the build environment, tools, compilers and so on.
-
-## Steps to test or reproduce
-
-Outline the steps to test or reproduce the PR here.
+- [ ] Fix
+- [ ] Refactor
+- [ ] New Target
+- [ ] Feature