[INFRA] improve issue and pull request templates (#366)

- issue: don't display link that allow the creation of blank issue (encourage
  contributors to use issue templates)
  - pull request: fix typo + improve 'link to issue' explanation

.github/ISSUE_TEMPLATE/config.yml

@@ -0,0 +1,2 @@
+# see https://help.github.com/en/github/building-a-strong-community/configuring-issue-templates-for-your-repository#configuring-the-template-chooser
+blank_issues_enabled: false

.github/pull_request_template.md

@@ -5,17 +5,19 @@ Failure to do so may result in the rejection of the Pull Request.
 
 Put the title like `[KIND OF CHANGE] SHORT DESCRIPTION`
 
-*KIND OF CHANGE* can be:
-- Infra
-- Bug
-- Feat
+*KIND OF CHANGE* can be (see existing Pull Request for more elements):
+- DOC
+- FEAT
+- FIX
+- INFRA
+- REFACTOR
 ...
 
 **Details**
 
 Explain the **details** for making this change: What existing problem does the Pull Request solve? Why is this feature beneficial?
 
 
-**On automtatic closing of ISSUES**
+**On automatic closing of ISSUES**
 
-Put `closes #XXXX` in your comment to auto-close the issue that your PR fixes (if such).
+Put `closes #XXXX` (remove backticks to let GitHub create the link) in your comment to auto-close the issue that your PR fixes (if such).