Update configuring_zed__key_bindings.md (#7310)

Added explanations for binding `null` to a keyboard binding.

Release Notes:

- N/A

docs/src/configuring_zed__key_bindings.md

@@ -33,6 +33,25 @@ You can see more examples in Zed's [`default.json`](https://zed.dev/ref/default.
 
 _There are some key bindings that can't be overridden; we are working on an issue surrounding this._
 
+## Special Keyboard Layouts
+Some people have unique and custom keyboard layouts.
+
+For example, [@TomPlanche](https://github.com/TomPlanche) having a [French keyboard](https%3A%2F%2Fcdn.shopify.com%2Fs%2Ffiles%2F1%2F0810%2F3669%2Ffiles%2Ffrench-azerty-mac-keyboard-layout-2021-keyshorts.png&f=1&nofb=1&ipt=f53a06c5e60a20b621082410aa699c8cceff269a11ff90b3b5a35c6124dbf827&ipo=images), had to type `Shift-Alt-(` in order to have a simple `[` so he made a simple layout with those 'rules':
+`ù -> [`, `backtick -> ]`, `Alt-[ (where [ is the old ù) -> {`, `Alt-] -> }`.
+But, it was impossible to take into account the `{` and `}` when he was typing so now, in order to ignore a binding, he can add `null` to the binding: 
+```json
+[
+    {
+        "context": "Editor",
+        "bindings": {
+          "alt-[": null,
+          "alt-]": null,
+        }
+    }
+]
+```
+
+
 ## All key bindings
 
 ### Global