Update Parsing.fs

Author: Happypig375

src/FSharpPlus/Parsing.fs

@@ -33,7 +33,7 @@ module Parsing =
                 | 'B' -> "([01]+)"
                 | 'c' -> "(.)"
                 | 'd' | 'i' -> "([+-]?[0-9]+)"
-                | 'e' | 'E' | 'f' | 'F' | 'g' | 'G' | 'M' -> "([+-]?[0-9.]+(?:[eE][+-]?[0-9]+)?)"
+                | 'e' | 'E' | 'f' | 'F' | 'g' | 'G' | 'M' -> "([+-]?[0-9]+(?:\.[0-9]+)?(?:[eE][+-]?[0-9]+)?)"
                 | 'o' -> "([0-7]+)"
                 | 'u' -> "([0-9]+)"
                 | 's' -> "(.*?)"