gpu: update CommandEncoder.clearBuffer defaults/optionality

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

gpu/src/command_encoder.zig

@@ -21,6 +21,8 @@ pub const CommandEncoder = *opaque {
         return Impl.commandEncoderBeginRenderPass(command_encoder, descriptor);
     }
 
+    // Default `offset`: 0
+    // Default `size`: `gpu.whole_size`
     pub inline fn clearBuffer(command_encoder: CommandEncoder, buffer: Buffer, offset: u64, size: u64) void {
         Impl.commandEncoderClearBuffer(command_encoder, buffer, offset, size);
     }