Package lacks command line functionality due to missing Main.java

[yegor256]

Currently, this repository is a Java package. However, we can add Main.java to it and turn it into an executable JAR. This will allow us to use it in command line like a traditional linter. It should print warnings in either text, XML, or SARIF format.

Motivated by objectionary/eo-lsp-server#47

[Thayorns]

@yegor256 Good day!

I would be very grateful if you could clarify the situation around this #700 PR.