Add a Shortcut "Tab button" to Toggle Between Object and World Shader Contexts

Proposal

Add a keyboard shortcut that toggles between the Object and World shader contexts when the Shader Editor is the active editor.

I suggest using Tab as the default shortcut because it is commonly used as a quick toggle between related modes or contexts. Since the Shader Editor is a different editor from the 3D Viewport, this shortcut would only be active when the Shader Editor has focus.

If using Tab by default is not appropriate due to existing keymap conventions, the shortcut could instead be user-configurable.