Proposal: Add marketplace link to auto-generated header

[mrlacey]

I think it would be helpful to include the marketplace link in the header of the generated files.

I'm using this in a project where we want to help encourage community contributions by making it as easy as possible for people to contribute. Having an extension installed as a requirement is a concern, but adding something to the code to clarify what's needed and where to get it from helps lessen this concern.

So, instead of having a header like this (the current behavior):

// ------------------------------------------------------------------------------
// <auto-generated>
//     This file was generated by VSIX Synchronizer
// </auto-generated>
// ------------------------------------------------------------------------------

It would look like this:

// ------------------------------------------------------------------------------
// <auto-generated>
//     This file was generated by VSIX Synchronizer
//     Available from https://marketplace.visualstudio.com/items?itemName=MadsKristensen.VsixSynchronizer64
// </auto-generated>
// ------------------------------------------------------------------------------

If linking to one of the 64 OR 32-bit versions is a concern, it could include a link to a marketplace search that returns both: https://marketplace.visualstudio.com/search?term=%22vsix%20synchronizer%22&target=VS

I'll happily submit a PR for this change, but I recognize the benefit of discussing this idea first.