Rename the module to glsl-matcap

Hi guys,
As I'm sure you know, most glsl functions on npm are prefixed with `glsl` I think a rename would be good for consistency, and it also makes it clearer for an external viewer what this package relates to.
Thanks,
Alvin

Start by locating the package name and npm metadata for matcap, then search the repository for references to the current module name. Update the package identity to glsl-matcap and verify that repository references remain consistent; the issue provides no specific test or file to run.

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