Add tooltips with hotkeys for main screens buttons

[gmikhail]

I suggest adding tooltips with hotkeys for main screens buttons.

• The main purpose is to show keyboard shortcuts.
• This will also make the behavior of the main interface more uniform and predictable.

Right now tooltips are only available for playtest buttons.

Now, if a beginner starts reading the documentation in order, he will learn about the Ctrl + F1 ... F4 combination only in the category Getting Started / Step by step / Using signals, in which this shortcut is mentioned for the first time. Which is a little counterintuitive. It makes more sense to mention these shortcuts earlier, in Getting Started / Introduction / First look at Godot's editor.

In any case, a simple tooltip with a keyboard shortcut when hovering the mouse over a button will be useful for everyone.

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I looked at Godot's source code and didn't find a quick solution for this. Therefore, I decided to open a discussion, for those who are better familiar with the engine architecture, adding this feature will not be a big problem.

As tooltips, you can use ready-made strings and shortcuts specified in editor/editor_node.cpp

ED_SHORTCUT_AND_COMMAND("editor/editor_2d", TTR("Open 2D Editor"), KeyModifierMask::CTRL | Key::F1);
ED_SHORTCUT_AND_COMMAND("editor/editor_3d", TTR("Open 3D Editor"), KeyModifierMask::CTRL | Key::F2);
ED_SHORTCUT_AND_COMMAND("editor/editor_script", TTR("Open Script Editor"), KeyModifierMask::CTRL | Key::F3);
ED_SHORTCUT_AND_COMMAND("editor/editor_assetlib", TTR("Open Asset Library"), KeyModifierMask::CTRL | Key::F4);

ED_SHORTCUT_OVERRIDE("editor/editor_2d", "macos", KeyModifierMask::META | KeyModifierMask::CTRL | Key::KEY_1);
ED_SHORTCUT_OVERRIDE("editor/editor_3d", "macos", KeyModifierMask::META | KeyModifierMask::CTRL | Key::KEY_2);
ED_SHORTCUT_OVERRIDE("editor/editor_script", "macos", KeyModifierMask::META | KeyModifierMask::CTRL | Key::KEY_3);
ED_SHORTCUT_OVERRIDE("editor/editor_assetlib", "macos", KeyModifierMask::META | KeyModifierMask::CTRL | Key::KEY_4);

So that the final tooltips look like this in the editor (naturally with different shortcuts for different OS)

Open 2D Editor (Ctrl+F1)
Open 3D Editor (Ctrl+F2)
Open Script Editor (Ctrl+F3)
Open Asset Library (Ctrl+F4)