feat: output tag name and upload url

[mmarchini]

The tag name is useful to interact with the release on following steps,
and the upload url is useful to upload assets to the release.

Fix: #8
Fix: #41

[bcoe]

@mmarchini thank you for the contribution 👌

[bcoe]

@mmarchini tagged release@1.4.0

[jef]

what does tag_name and upload_url look like? we can update some doc around the change. thanks for putting this out!

[mmarchini]

Both are equal to their respective values in the Create Release API response. The tag_name is the tag name (not to be mistaken with the release name), and the upload_url is an URL to the upload asset API endpoint. Agreed we should add some documentation, maybe an extra section in the readme with all values set in the output of the action.