Funding/Grant Form -Add to NixOS front page + create template via github

[refroni]

• Add a section of how to get the reimbursement to the funding/grant page

[zimbatm]

@domenkozar I suggested moving the funding applications to issue templates on this repo so that they can be processed like the rest of our inbound requests. Any objections?

[domenkozar]

I've spent quite some time setting the current infra up, but no objections if you'd like to do it :)

[zimbatm]

Thanks, I think it will allow us to iterate on the process more quickly. I'll take care of it.

[zimbatm]

Here is a preview of how it looks like: https://github.com/NixOS/foundation/issues/new?assignees=zimbatm&labels=funding-request%2Ctriage&template=funding_form.yml&title=%5BFunding%5D%3A+%24event+name+%24date