Docs: Add JSHint W047 compat to no-floating-decimal (#11861)

This ESLint rule handles both leading and trailing decimal points.
In order to ease discovery of this ESLint rule, mention the latter
warning as well, as users might only find those in their code.

https://github.com/jshint/jshint/blob/7993101/src/style.js#L100-L116

docs/rules/no-floating-decimal.md

@@ -40,4 +40,4 @@ If you aren't concerned about misinterpreting floating decimal point values, the
 
 ## Compatibility
 
-* **JSHint**: W008
+* **JSHint**: W008, W047