Fix snippet warning

[ihalila]

VSCode kept giving a warning related to a snippet:

The "New ScalaTest suite"-snippet very likely confuses snippet-variables and snippet-placeholders. See https://code.visualstudio.com/docs/editor/userdefinedsnippets#_snippet-syntax for more details.

So I went ahead and fixed the warning by changing both that and the "Add Sbt resolver" snippet to use placeholders instead. It makes using the snippets more useful too as you can just tab through the places where you need to type in stuff.

[ihalila]

A damn I accidentally included the laodConfig fix in this branch too, I'll remove that and open a pull request with just the snippet change.