Misc - Add default meta.cpp for Steam Workshop association (#469)

**When merged this pull request will:**
Make sure servers running this mod will associate it with the Steam
Workshop item for easier download while joining with the Arma 3 Launcher
or other third party tools.

### IMPORTANT

- [Development Guidelines](https://ace3.acemod.org/wiki/development/)
are read, understood and applied.
- Title of this PR uses our standard template `Component -
Add|Fix|Improve|Change|Make|Remove {changes}`.

meta.cpp

@@ -0,0 +1,2 @@
+protocol = 1;
+publishedid = 2020940806;