create issue template

[ligi]

cc @bumblefudge

[bumblefudge]

As per our conversation last week, @ligi , I think a little bit of structure can go a long way towards helping organizers set agendas more easily. Here are some suggestions:

Some possible questions for issue template:

• does this apply across many/all CAIPs or is this specific to one?
  • --> Prefix in issue name
• is this timely (a bug report, a hot fix, an ambiguity in an existing CAIP), or a long-term contribution/conversation?

Some possible questions for a PR template:

• is this a new CAIP?
  • if so, is it modelled on another? if so, which? did you consider PRing or iterating/superceding it to make it a multi-chain CAIP, if you recycled large portions of it?
• does this PR affect an accepted CAIP?
  • if so, have you discussed it with those