Pass down functions.ignore values in firebase.json to functions emulator

[dikatok]

Pass down functions.ignore values in firebase.json to functions emulator so that supposedly ignored directories/files will not trigger reload.

[dikatok]

Whoops, apparently I forgot to checkout my new branch and committed the changes to the master branch of my fork, is that okay?

[joehan]

Thanks for the contribution! Lgtm, but could you add an entry to changelog.md for this change?

[dikatok]

@joehan do you mean changelog.md in the root directory? is it supposed to be empty?

edit: ah is it reset on every release?

edit2: done