Suggestion: Use `deployment-status` action as `runs.post` script

[LeoColomb]

Both deployment-action and deployment-status are useful and works nicely together.
But using both of them comes with a duplication of the configuration data, and make the workflow a bit too complex.

GitHub Actions support a nice (actually quite common) feature: runs.post.
The most obvious usage of this feature is for caching data at the end of a job, like actions/setup-node.

Using this with deployment-action could be very valuable as well:

• Only one additional input would be sufficient to enable (or disable) the status submission
  • All the rest of the configuration is done only once
• It runs at the end of the job per default wherever the deployment is created
• The status of the job is available to the post script, not limited to success only