Encourage using raw strings in registry docs

[spenserblack]

This is a bit of a nitpick on how to write strings when they contain Windows-like paths. Generally, I think that raw strings are preferable in this scenario because

• It's a bit easier to read and more familiar (it looks like what you would write in cmd.exe).
• It prevents accidentally escaping a character by writing \ instead of \\. I think that characters like newlines (\n), tabs (\t), etc. are rare enough in paths that this is a reasonable trade-off.

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I noticed a lot of other places where there were strings with \\ that could be converted to raw strings. If this stylistic change makes sense, I can convert all of those if wanted. Right now I was just focusing on the documentation that I was reading.

[kennykerr]

Thanks for the contribution! This seems reasonable for docs. I wouldn't be in favor of widespread changes just for the sake of using raw string literals. That could amount to a lot of churn for little benefit.