[RFE] ci: Avoid running workflow when not needed

[blanquicet]

For instance, PR #27 only updated README and the krew manifest. In that case, workflow doesn't need to run. Same if only files under docs are modified, etc.

[mqasimsarfraz]

One possible implementation can be to use paths filter to trigger the CI e.g:

on:
  pull_request:
    paths:
      - '**.yml'
      - '**.go'
      - 'go.mod'
      - 'go.sum'
  push:
    branches:
      - main
    tags:
      - 'v*'

Or may be we are allowed to exclude paths using paths as well?

[blanquicet]

I would also include Makefile and yaml (we have config.yaml but exclude .krew.yaml).