Add README note

Author: iansan5653

README.md

@@ -109,7 +109,8 @@ for (const el of document.querySelectorAll('[data-shortcut]')) {
    1. `"Mod+"` can appear in any order in a hotkey string. For example: `"Mod+Alt+Shift+KEY"`
    2. Neither the `Control` or `Meta` modifiers should appear in a hotkey string with `Mod`.
    3. Due to the inconsistent lowercasing of `event.key` on Mac and iOS when `Meta` is pressed along with `Shift`, it is recommended to avoid hotkey strings containing both `Mod` and `Shift`.
-7. You can use the comma key `,` as a hotkey, e.g. `a,,` would activate if the user typed `a` or `,`. `Control+,,x` would activate for `Control+,` or `x`.
+7. `"Plus"` and `"Space"` are special key names to represent the `+` and ` ` keys respectively, because these symbols cannot be represented in the normal hotkey string syntax.
+8. You can use the comma key `,` as a hotkey, e.g. `a,,` would activate if the user typed `a` or `,`. `Control+,,x` would activate for `Control+,` or `x`.
 
 ### Example