Add issue templates

[stefanprodan]

This repo should have its own issue templates instead of https://github.com/fluxcd/.github/pull/3

[rishabh96b]

/label good-first-issue

[kingdonb]

/assign @kingdonb

I can work on this

[alisondy]

for people editing docs remind people to check over the style guide assign reviewers

[harshitasao]

Hi @stefanprodan, I'd like to work on this issue!