Improvement on github CI actions to test build process

[berinhard]

The version 0.7.2 was broken because the build package didn't have the required templates and static files in order for the serve command to work. The issue was caused because I had to rename the http app to http_local (more about this in #220).

The problem was fixed in 0.7.3 by updating the the manifest and setup files (more in 14be8d5).

To avoid this to happen again, we could add a linux script that would:

• run python3 setup.py sdist bdist_wheel;
• check if all the assets/template files are present in the final build;

If not, the build should fail and, thus, the PR cannot be merged.