Use recommended release strategy

[damccorm]

We should be using the release strategy specified by https://github.com/actions/toolkit/blob/master/docs/action-versioning.md#recommendations

To get there, we need to:

1. Create a releases/v1 branch and move the v1 tag and future releases there
2. Warn that we will deprecate the master branch and that you should attach to v1 instead. We will support master in a warned but deprecated state for ~1 month.
3. Switch the warning to an error on master. Remove node_modules from the master branch. We will stay in this state for ~1 month.
4. Remove the error on master.

During steps 2 and 3, we need to be extra careful to not check the warning/error into the releases branch.

[bryanmacfarlane]

We're not doing this. Instead, we're moving toward ncc and packing. Will open a separate issue