Add repo issue templates

[HGWright]

Stratify > Insights > Community Standards

See GitHub docs

[HGWright]

Issue templates have been added. @bjlittle you are more than welcome to, but not required to have a look and suggest changes if necessary. I will close this soon if I don't hear and changes.

[bjlittle]

@HGWright Awesome!

Looks great!

My only suggestion would be on the style choice on title capitalisation e.g., see https://www.grammarly.com/blog/capitalization-in-the-titles/

For iris we have:

Also, I'd suggest dropping the using of template in the Custom issue template:

Also, akin to iris, you may want to also add links to the python-stratify GH Discussions. Your call 👍