Add Vanta required PR and Issue templates

[thraxil]

All repos must have PR and Issue templates now. These aren't perfect, but are something to start with.

[OmarIthawi]

Thanks Anders.

• I've changed the default branch of this repo to juniper.
• I've rebased over juniper.
• I've pushed-force.
• I'll merge before once the CI passes.

[OmarIthawi]

I'm merging this doc-only PR even though the CI didn't pass.