Make the template more generic

[HHK1]

We have this template popping up in some python repos, or infra repos.

I think it can be made a bit more generic to be really useful.

I tried to submit a PR, but I don't have write rights (should also be fixed)

Here is my suggestion:

_This is the default pull request template. You can customize it by adding a `pull_request_template.md` at the root of your repo or inside the `.github` folder._

# Jira Ticket

_Include a link to your Jira Ticket_
_Example: [JIRAISS-1234](https://spotinst.atlassian.net/browse/JIRAISS-1234)_

# Demo

_Please add a recording of the feature/bug fix in work. if you added new routes, the recording should show the request and response for each new/changed route_

# Checklist:

- [ ] My code follows the style guidelines of this project
- [ ] I have performed a self-review of my own code
- [ ] I have validated all the requirements in the Jira task were answered
- [ ] I have all neccessary approvals for the design/mini design of this task
- [ ] (**For public services only**) I have approved the API changes and granular permission patterns (documentation subtask)

And the commit message I tried to push:

Date:   Fri Dec 10 13:19:38 2021 +0100

    update the default template to be more generic

    - Use the special markup _ _ to show the instructions only when editing
    the pull request description
    - Add a notice on how to override this template per repo
    - Update the checklist to be more generic

[HHK1]

@snir102002