glfw: add modifier key flags

Signed-off-by: Stephen Gutekanst <stephen@hexops.com>

glfw/src/mod.zig

@@ -0,0 +1,23 @@
+//! Modifier key flags
+//!
+//! See glfw.SetKeyCallback for how these are used.
+
+const c = @cImport(@cInclude("GLFW/glfw3.h"));
+
+/// If this bit is set one or more Shift keys were held down.
+pub const shift = C.GLFW_MOD_SHIFT;
+
+/// If this bit is set one or more Control keys were held down.
+pub const control = C.GLFW_MOD_CONTROL;
+
+/// If this bit is set one or more Alt keys were held down.
+pub const alt = C.GLFW_MOD_ALT;
+
+/// If this bit is set one or more Super keys were held down.
+pub const super = C.GLFW_MOD_SUPER;
+
+/// If this bit is set the Caps Lock key is enabled and the glfw.lock_key_mods input mode is set.
+pub const caps_lock = C.GLFW_MOD_CAPS_LOCK;
+
+/// If this bit is set the Num Lock key is enabled and the glfw.lock_key_mods input mode is set.
+pub const num_lock = C.GLFW_MOD_NUM_LOCK;