tests(ci): authenticate protoc download

[brendankenny]

running into github api rate limiting errors when downloading protoc, which is weird because it's github making the request. Turns out we need to supply a token :)

arduino/setup-protoc#6

Also drops CI runs on push

[patrickhulce]

LGTM

[paulirish]

should we lock to this version of the action so we dont leak the token to whatever lands in their master tomorrow?

i think arduino/[email protected] will work? if not we'll need to ask them to rls

[paulirish]

jk we can do a specific commit: arduino/setup-protoc@7ad700d

thx https://help.github.com/en/actions/reference/workflow-syntax-for-github-actions#jobsjob_idstepsuses

[patrickhulce]

oh that's so cool! it never occurred to me that github actions can keep secrets from being in the environment already unlike travis. that's dope :)

[paulirish]

Here's where the token ends up being used: https://github.com/arduino/setup-protoc/blob/7ad700d3b20e2a32b35d2c17fbdc463891608381/lib/installer.js#L125-L136