issue running an example

when attempted to run example provided at https://github.com/charmbracelet/harmonica/blob/master/examples/spring/opengl/main.go
returns error as below. wondering if am missing to install any package ?

```
(base) ➜ temp go run main.go
# pkg-config --cflags -- gl gl
Package gl was not found in the pkg-config search path.
Perhaps you should add the directory containing `gl.pc'
to the PKG_CONFIG_PATH environment variable
No package 'gl' found
Package gl was not found in the pkg-config search path.
Perhaps you should add the directory containing `gl.pc'
to the PKG_CONFIG_PATH environment variable
No package 'gl' found
pkg-config: exit status 1
# github.com/go-gl/glfw/v3.3/glfw
vendor/github.com/go-gl/glfw/v3.3/glfw/c_glfw.go:4:10: fatal error: glfw/src/context.c: No such file or directory
4 | #include "glfw/src/context.c"
| ^~~~~~~~~~~~~~~~~~~~
compilation terminated.

```