Add EnumFlags.from

src/EnumFlags.zig

@@ -10,6 +10,12 @@ pub fn EnumFlags(comptime E: type) type {
 
         pub const empty: Self = .{ .data = 0 };
 
+        pub fn from(mask: BackingInt) Self {
+            return .{
+                .mask = mask,
+            };
+        }
+
         pub fn contains(self: Self, flag: E) bool {
             return (self.mask & @intFromEnum(flag)) != 0;
         }