Load from known directory

[mrlacey]

From https://marketplace.visualstudio.com/items?itemName=MattLaceyLtd.DemoSnippets&ssr=false#review-details

This is a really useful extension - I actually use this not just for demos, but as an alternative to code snippets, which are not very implemented within Visual Studio. One suggestion I would make for this scenario would be to optionally be able to load from a known directory when Visual Studio is started, rather than requiring them to be added to every project in order for them to be used.