Add option 'path-type'

[eine]

Fix #13

In this PR, two procedures to override the default value of MSYS2_PATH_TYPE are provided. On the one hand, if users set the environment variable, it is not overwritten. On the other hand, option pathType can be used to set the default. Supported values are strict, inherit, or any other (minimal).

Two tests are added to the workflow, one for each procedure.

BTW, @actions/core is updated.

[Ecco]

Great, thanks! I think the syntax in the YAML file should rather be file-type instead of fileType. Just like runs-on is not runsOn.

[eine]

Great, thanks! I think the syntax in the YAML file should rather be file-type instead of fileType. Just like runs-on is not runsOn.

Done!

[Ecco]

Great, thanks!

[eine]

@Ecco, would you mind updating v1, and optionally releasing a semver tag (https://github.com/actions/toolkit/blob/master/docs/action-versioning.md#versioning), so that this feature and update are available?