ResourceFormatLoader: note needs better wording

**Your Godot version:**
4.3 stable

**Issue description:**
> "Note: You can also extend [EditorImportPlugin] if the resource type you need exists but Godot is unable to load its format. Choosing one way over another depends on if the format is suitable or not for the final exported game. For example, it's better to import .png textures as .ctex ([CompressedTexture2D] first, so they can be loaded with better efficiency on the graphics card."

The meaning of this line is especially unclear: "if the resource type you need exists but Godot is unable to load its format" which erroneously directed a user to extend ResourceFormatLoader when EditorImportPlugin was more appropriate:

**from Discord:**
> The reason I started on extending ResourceFormatLoader instead is because of the following statement in it's docs which left me with the impression that ResourceFormatLoader was the way to go because as far as I know there is no plain text resource in Godot.

**URL to the documentation page (if already existing):**
https://docs.godotengine.org/en/stable/classes/class_resourceformatloader.html#description