discuss commit guidelines

We should probably discuss how we want commit styling and signoff.

i.e. No-one in node core commits without review, but I am not 100% sure that is necessary here.

Example of a node core commit:

```
doc: say hello in under 50 chars

description in under 72 chars/line

Fixes:
PR-URL:
Reviewed-By: Name
```

cc @expressjs/express