feat: Adding a webXR primer tutorial

[taeuscherpferd]

Changes

• Added a new tutorial page and embedded a link to the CodeSandbox with the WebXR primer project
• Updated eslint rule to match the correct current syntax
• Bumped all of the navigation numbers so that the paging continues to work correctly

[taeuscherpferd]

• Url to CodeSandbox for reference

[taeuscherpferd]

@bbohlender I've moved this from codesandbox to the examples, updated the yml to build and host it on github, and updated the iframe in the tutorial section to point there. As I've never created an example in the examples before, I'm not sure if I missed anything there, so keep an eye out for that during the code review. Thanks! 👍