[MSOURCES-113] Store source encoding info in a standard file

**[Fred Bricon](https://issues.apache.org/jira/secure/ViewProfile.jspa?name=fbricon)** opened **[MSOURCES-113](https://issues.apache.org/jira/browse/MSOURCES-113?redirect=false)** and commented

It'd be nice if IDEs were able to automatically set proper source encoding when attaching sources to project dependencies. 

In eclipse/m2e, we tried to automatically detect encoding but it didn't work out https://git.eclipse.org/r/#/c/116390/

A more reliable way would be to ensure the encoding info was stored inside the source archive, so that IDEs could peek into it and ensure proper settings.

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No further details from [MSOURCES-113](https://issues.apache.org/jira/browse/MSOURCES-113?redirect=false)