Add support for WebGL2 clear buffer operations

Adds support for the following WebGL2 methods:

- `clearBufferfv`
- `clearBufferiv`
- `clearBufferuiv`
- `clearBufferfi`

See: https://www.khronos.org/registry/webgl/specs/latest/2.0/#3.7.11

components/canvas_traits/webgl.rs

@@ -529,6 +529,10 @@ pub enum WebGLCommand {
     GetSamplerParameterInt(WebGLSamplerId, u32, WebGLSender<i32>),
     BindBufferBase(u32, u32, Option<WebGLBufferId>),
     BindBufferRange(u32, u32, Option<WebGLBufferId>, i64, i64),
+    ClearBufferfv(u32, i32, Vec<f32>),
+    ClearBufferiv(u32, i32, Vec<i32>),
+    ClearBufferuiv(u32, i32, Vec<u32>),
+    ClearBufferfi(u32, i32, f32, i32),
 }
 
 macro_rules! nonzero_type {