Added Keybindings to README (#751)

* Update README.md

Added keybindings

* Update README.md

Author: Riz-waan

README.md

@@ -51,6 +51,10 @@ This extension provides several commands in the Command Palette (<kbd>F1</kbd> o
 - **Arduino: Upload Using Programmer**: Upload using an external programmer.
 - **Arduino: Verify**: Build sketch.
 
+## Keybindings
+- **Arduino: Upload** <kbd>Alt</kbd> + <kbd>Cmd</kbd> + <kbd>U</kbd> *or* <kbd>Alt</kbd> + <kbd>Ctrl</kbd> + <kbd>U</kbd>
+- **Arduino: Verify** <kbd>Alt</kbd> + <kbd>Cmd</kbd> + <kbd>R</kbd> *or* <kbd>Alt</kbd> + <kbd>Ctrl</kbd> + <kbd>R</kbd>
+
 ## Options
 | Option | Description |
 | --- | --- |