GitHub: sync GitHub templates and actions from optee_os

The GitHub templates and actions are useful to the "build" git also,
therefore recursively sync up (copy) the .github folder from optee_os.

Note, that here we have also done some changes to the GitHub actions. In
optee_os we have two different actions files, one for issues and one for
pull requests. It seems like it is possible to combine them into a
single action file as shown in the actions examples [1]. Another change
is that we also exclude marking issues stale if they already have the
label "bug". Note that we're only excluding issues, since PR's should
not have the "bug" label to start with.

Link: [1] https://github.com/actions/stale/blob/master/README.md



Signed-off-by: Joakim Bech <joakim.bech@linaro.org>
Acked-by: Jens Wiklander <jens.wiklander@linaro.org>
Acked-by: Jerome Forissier <jerome@forissier.org>

.github/issue_template.md

+<!--
+    General guidance when creating issues:
+
+    1. Please try to remember to close the issue when you have
+       got an answer to your question.
+
+    2. It never hurts to state which commit or release tag you are using in case
+       the question is about build issues.
+
+    3. Try to use GitHub markdown formatting to make your issue more readable:
+         https://help.github.com/articles/basic-writing-and-formatting-syntax/#quoting-code
+
+    4. Try to search for the issue before posting the question:
+         -> Issues tab -> Filters
+
+    5. Check the FAQ before posting a question:
+         https://optee.readthedocs.io/faq/faq.html
+
+    NOTE: This comment will not be shown in the issue, so no harm keeping it,
+    but feel free to remove it if you like.
+-->

.github/pull_request_template.md

+<!--
+    If you are new to submitting pull requests to OP-TEE, then please have a
+    look at the list below and tick them off before submitting the pull request.
+
+    1. Read our contribution guidelines:
+         https://optee.readthedocs.io/general/contribute.html
+
+    2. Read the contribution section in Notice.md and pay extra attention to the
+       "Developer Certificate of Origin" in the contribution guidelines.
+
+    3. You should run checkpatch preferably before submitting the pull request.
+
+    4. When everything has been reviewed, you will need to squash, rebase and
+       add tags like `Reviewed-by`, `Acked-by`, `Tested-by` etc. More details
+       about this can also be found on the link provided above.
+
+    NOTE: This comment will not be shown in the pull request, so no harm keeping
+    it, but feel free to remove it if you like.
+-->

.github/workflows/stale_issue.yml

+name: "Close stale issues"
+on:
+  schedule:
+  - cron: "15 00 * * *"
+
+jobs:
+  stale:
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/stale@v1
+      with:
+        repo-token: ${{ secrets.GITHUB_TOKEN }}
+        stale-issue-message: 'This issue has been marked as a stale issue because it has been open (more than) 30 days with no activity. Remove the stale label or add a comment saying that you would like to have the label removed otherwise this issue will automatically be closed in 5 days. Note, that you can always re-open a closed issue at any time.'
+        stale-pr-message: 'This pull request has been marked as stale because it has been open (more than) 30 days with no activity. Remove the stale label or add a comment saying that you would like to have the label removed otherwise this pull request will automatically be closed in 5 days. Note, that you can always re-open a closed pull request at any time.'
+        exempt-issue-label: 'bug'
+        days-before-stale: 30
+        days-before-close: 5