Improve readme - make example more readable/copy pasteable

[JanMikes]

Hi, it is not possible to just copy/paste action example as it is in json format instead of yaml.

Improving it would make easier decision whether i will use this action or not :-)

[JanMikes]

As well it is not clear, whether it installs it so i can use in next steps or not:

- uses: juankaram/sentry@master

- run: sentry-cli releases new -p project1 -p project2 $VERSION