Add notice field to modules

[lucacasonato]

Modules should get a optional notice field that can only be set manually by us. The type of this field should be string or undefined, and should not be changeable by webhooks. It should be initially unset. The field should be present in the /modules/:name api response.

This field will be used to display notices about a certain module on the deno.land/x website, for example that instead of using https://deno.land/x/istrue, you should use value === true.

[wperron]

I understand the impulse, I really do, but I'm hesitant to implement this -- the notice field would be applied arbitrarily by the maintainers of the registry, thus making making a judgement call on what a "good module" constitutes. If the notice was based on an objective and measurable metric I'd be much more inclined to support it (maybe sloc? number of files?)

[erfanium]

#57 May fix this