Use glFlush instead of glFinish

glFinish waits for all GPU rendering to complete. This can stall the
rendering pipeline. In comparison, glFlush just inserts a synchronization
barrier, which is enough for our usage.

backend: fix format string for view resolution

XR_MND_EGL_ENABLE_EXTENSION_NAME -> MNDX

Seems like this extension has been renamed.

build: disable FreeRDP in wlroots

It causes warnings.

Fix invalid imageArrayIndex value

xrutil: add two new enum items to wxrc_xr_result_str

Update video link

Add README.md

Discard fragments in cube shader

Discard fragments in grid shader

This prevents the depth buffer from being polluted with samples for
holes between grid lines.

Use glDepthMask instead of glDepthFunc

This allows us to correctly composite views with the 3D scene, while
still preventing collisions between two views.

Add depth buffer to XR views

Enable depth buffer

Add buffer type to zxr-shell-unstable-v1.xml

And update our implementation to consider it. This does not add a depth
buffer to wxrc, it just adds it to the state tracker for the XR shell
protocol.

Rig up seat clipboard operations

Fix view_at logical view sorting

Should be done front-to-back and should exit early once a matching view
is found.

Add wlr-data-control and wp-primary-selection

Use logical distance for view_at

As opposed to spatial distance. We will likely want to change this later
for 3D views.

Implement resize with mod+right

Fix views setting NULL cursor