fix(cli): init command

[ematipico]

Summary

Fixes #1515

There were few issues that I fixed here:

• the check on arguments is now dropped, because it's not needed;
• fixed the check hasProject.data;
• handled the case where the user inserts 0 as value for the tab size;
• add manually the project to the ProjectManager;
• changed the way the manifest of the project is retrieved. Before, we were interrogating the file system, although now we can't retrieve anymore from there (probably it changed recently). We now retrieve the manifest manually as we already have all the information we need;
• defaulting some values inside the .editorconfig. This fixes the case where we have empty a project with no files at all, Rome would create an empty file, which is not what we want. So, in case we don't have any extension, we set some defaults.

Test Plan

Manually checked