gpu: add CompareFunction enum

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

gpu/src/types.zig

@@ -50,3 +50,15 @@ pub const BlendOperation = enum(u32) {
     min = 0x00000003,
     max = 0x00000004,
 };
+
+pub const CompareFunction = enum(u32) {
+    undef = 0x00000000,
+    never = 0x00000001,
+    less = 0x00000002,
+    less_equal = 0x00000003,
+    greater = 0x00000004,
+    greater_equal = 0x00000005,
+    equal = 0x00000006,
+    not_equal = 0x00000007,
+    always = 0x00000008,
+};