Add a chapter to the XR manual that improves the startup script.

[BastiaanOlij]

This PR adds a new chapter to the XR manual detailing the contents of our enhanced startup script that we used in our XR demos in the Godot demos repository.

Our introduction contains a bare minimum script that forms the basis for all XR interfaces. This script adds specific details for OpenXR only and adds further context to a number of signals emitted by the OpenXR interface.
It also has further details on the unique nature of refresh rates on XR headsets and how to properly set things up.

[skyace65]

Finally read through everything, the instructions and explanations made sense. Not seeing any grammar errors.

There's a ton of lines that need to be broken up into multiple lines though:
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[BastiaanOlij]

There's a ton of lines that need to be broken up into multiple lines though:

Don't things just wrap automatically? Happy to start every sentence on a new line but generally I stick to paragraphing of information that belongs together. Formatting is as much about conveying information as the actual text.

[skyace65]

They do but it makes it a bit harder to edit when everything is on one very long line, we don't have those anywhere else in the docs. I'm not sure I understand your point about paragraphing, When I say split into multiple lines I mean like lines 6 and 7 on this page, that's still one paragraph. I'm not asking you to break up those lines and add blank space between them, sorry if that wasn't clear.

[BastiaanOlij]

They do but it makes it a bit harder to edit when everything is on one very long line, we don't have those anywhere else in the docs. I'm not sure I understand your point about paragraphing, When I say split into multiple lines I mean like lines 6 and 7 on this page, that's still one paragraph. I'm not asking you to break up those lines and add blank space between them, sorry if that wasn't clear.

Ah, so it's not adding in a hard newline and break the flow.. Ok no problem, I can clean that up

[BastiaanOlij]

@skyace65 Let me know if it's better, the painful thing of making these changes is that all the line numbers change with it, so it was hard to check if I fixed all the places you identified :)

[skyace65]

Looks good now!

[skyace65]

Thanks!