[Keyboard navigation - MakeCode editor] make simulator a landmark & include a keyboard shortcut to reach it

[microbit-lucy]

Describe the bug If you are navigating by keyboard, you can use tab to navigate through the options in the MakeCode editor. Getting to/from the Simulator takes a lot of 'tabs'.

Blocks/toolbox shortcuts are being specified by Blockly but a simulator is not a regular Blockly feature. Making the simulator a landmark and creating a keyboard shortcut to reach it would be helpful.

To Reproduce Steps to reproduce the behavior:

1. Go to 'https://makecode.microbit.org/#editor'
2. Press tab and skip to the Java editor (as this is accessible but blocks aren't right now).
3. Toggle 'tab' behaviour (so it navigates options rather than adding a tab in your code) by pressing Control+M on Windows or Control+Shift+M on Mac (as described in the accessibility documentation).
4. Press shift+tab to get back to the Simulator (count how many shift+tabs it takes)

https://github.com/microsoft/pxt-microbit/assets/102724242/23595108-c4ac-42d4-bf6a-b698080cd64b

Expected behavior Make the Simulator a landmark (recognised by screen readers). Add a keyboard shortcut to jump to the simulator easily.

Additional context When keyboard navigation is implemented for blocks this will become more of an issue but it is still a problem for those using Javascript or Python already. There is already a shortcut to reach the toolbox (Control+Alt+T on Windows or ⌘+Alt+T on Mac) but not the simulator.