Update state of JS rule GCI31 in RULES.md

Author: utarwyn

RULES.md

@@ -43,7 +43,7 @@ Some are applicable for different technologies.
 | GCI28    | Optimize read file exceptions                                 |                                                                                                                                                                                                                                                                                                                                                                                                                               |                                                                                                                                                                         | ✅    | 🚫  | 🚫 | 🚫     | 🚫   | 🚫 | 🚫   |
 | GCI29    | Avoid usage of CSS animations                                 | ESLint key : @ecocode/avoid-css-animations /// type : Front-end                                                                                                                                                                                                                                                                                                                                                               |                                                                                                                                                                         | ❓    | ❓   | ✅  | ❓      | ❓    | ❓  | 🚫   |
 | GCI30    | Provide a print stylesheet                                    | ESLint key : @ecocode/provide-print-css /// type : Front-end                                                                                                                                                                                                                                                                                                                                                                  |                                                                                                                                                                         | ❓    | ❓   | ✅  | ❓      | ❓    | ❓  | 🚫   |
-| GCI31    | Prefer lighter formats for image files                        | ESLint key : ... /// type : ...                                                                                                                                                                                                                                                                                                                                                                                               |                                                                                                                                                                         | 🚧   | ❓   | 🚀 | ❓      | ❓    | ❓  | 🚀   | 
+| GCI31    | Prefer lighter formats for image files                        | ESLint key : ... /// type : ...                                                                                                                                                                                                                                                                                                                                                                                               |                                                                                                                                                                         | 🚧   | ❓   | ✅ | ❓      | ❓    | ❓  | 🚀   | 
 | GCI32    | Initialize builder/buffer with the appropriate size           | If you know in advance how many characters would be appended, initialize builder/buffer with the appropriate size. They will thus never have to be resized. This saves CPU cycles and therefore consumes less energy.                                                                                                                                                                                                         |                                                                                                                                                                         | ✅    | 🚫  | 🚫 | 🚫     | 🚫   | 🚫 | 🚫   |
 | GCI35    | Using try...catch calls (on File Not Found error)             | When an exception is thrown, a variable (the exception itself) is created in the catch block and destroyed at the end of the block.  Creating this variable and destroying it consumes CPU cycles and RAM unnecessarily. That is why it is important not to use this construction and to prefer, as much as possible, a logical test.  This new rule replace old GCI34 only for a particular use case (FileNotFoundException) | [cnumr best practices (3rd edition) BP_047 (no longer exists in edition 4)](https://www.greenit.fr/2019/05/07/ecoconception-web-les-115-bonnes-pratiques-3eme-edition/) | 🚫   | ✅   | 🚀 | ✅      | 🚀   | 🚫 | 🚫   |
 | GCI36    | Avoid autoplay for videos and audio content                   | Autoplaying media consumes unnecessary energy, especially when users might not be actively engaging with the content.                                                                                                                                                                                                                                                                                                         | [cnumr best practices BP_4003](https://github.com/cnumr/best-practices/blob/main/chapters/BP_4003_en.md)                                                                | 🚫   | 🚫  | ✅ | 🚫     | 🚫   | 🚫 | 🚧   |