v/.github/PULL_REQUEST_TEMPLATE

Please title your PR as follows: `time: fix foo bar`.

Explain what your PR does and why.

Do not use # to generate C code. This feature will be removed in a couple of days.

Squash commits into one if they refer to the same thing. Use `git rebase -i` for that.

Before submitting a PR, please run the tests with `make test`, and make sure V can still compile itself. Run this twice:

./v -o v
./v -o v

Thanks a lot for your contribution!