docs: update github templates

[sbliven]

Description

Updates the PR and issue templates

Motivation

PRs were failing the pr-title-checker action because the title format wasn't well documented. Rather than add this to our documentation, I think it is easier to just mention it in the PR template.

While I was doing that I also changed both templates to include instructions as comments. I think this is common in other github projects.

Changes:

• New github templates

Tests included

• Included for each change/fix? (N/A)
• Passing?

Documentation

• swagger documentation updated (required for API changes) (N/A)
• official documentation updated

official documentation info

I think the PR template is a better place for documentation than the other repo.

[sbliven]

One question: do we use the 'scope' part of titles for anything? Should we provide some guidelines about valid scicat scopes, or else remove this part of the regex entirely?

[sbliven]

BTW, this pr triggered by the test failure and subsequent discussion in #1442

[Junjiequan]

The scope part is very optional and it's just used to add extra information e.g, fix(authentication): some text, test(dataset): some API testetc. And I'm fine with either keepingor removing the scope regex.
I just hope people use Squash Merge more often so that the final commit message includes fix: feat: format from PR title automatically, as release changelogs are based on the commit message.

[Junjiequan]

Looks good to me