Add support for escape characters, make nuon a JSON superset (#4706)

* WIP

* Finish adding escape support in strings

* Try to fix windows

crates/nu-command/src/strings/parse.rs

@@ -48,7 +48,7 @@ impl Command for Parse {
             },
             Example {
                 description: "Parse a string using regex pattern",
-                example: "echo \"hi there\" | parse -r \"(?P<foo>\\w+) (?P<bar>\\w+)\"",
+                example: "echo \"hi there\" | parse -r '(?P<foo>\\w+) (?P<bar>\\w+)'",
                 result: Some(result),
             },
         ]