dca.ado needs a version number to be updateable from within Stata

Minor issue, but I downloaded dca in Stata to reproduce results in a paper. It’s not updateable from within Stata using `adoupdate`. Looking at the ado code, this is I think because it lacks the ‘version’ line. Usual convention is that the first line is something like
```*! X.Y Author name yyyy mm dd```
where the `*!` is what gets read by `adoupdate` and it will update if X.Y is a higher number than the current ado.