repo: support grunt tasks in proxy16 workflow

Standards checklist:

[x] The PR title is descriptive.
[x] The PR doesn't replicate another PR which is already open.
[x] The PR has self-explained commits history.
[x] The code is mine, or it's from somewhere with an Apache-2.0 compatible license.
[x] The code is efficient, to the best of my ability, and does not waste computer resources.
[x] The code is stable, and I have tested it myself, to the best of my abilities.
[x] If the code introduces new classes, methods, I provide a valid use case for all of them.

Related to PR #1175. Current PR must be merged first.