Update bindings for offscreenCanvas getContext

Author: nojaf

src/CanvasAPI/OffscreenCanvas.res

@@ -98,9 +98,9 @@ Returns null if the canvas has already been initialized with another context typ
 [Read more on MDN](https://developer.mozilla.org/docs/Web/API/OffscreenCanvas/getContext)
 */
 @send
-external getContext: (
+external getContext_2D: (
   offscreenCanvas,
-  ~contextId: offscreenRenderingContextId,
+  @as("2d") _,
   ~options: JSON.t=?,
 ) => offscreenCanvasRenderingContext2D = "getContext"
 
@@ -113,11 +113,11 @@ Returns null if the canvas has already been initialized with another context typ
 [Read more on MDN](https://developer.mozilla.org/docs/Web/API/OffscreenCanvas/getContext)
 */
 @send
-external getContext2: (
+external getContext_WebGL: (
   offscreenCanvas,
-  ~contextId: offscreenRenderingContextId,
-  ~options: JSON.t=?,
-) => imageBitmapRenderingContext = "getContext"
+  @as("webgl") _,
+  ~options: webGLContextAttributes=?,
+) => webGLRenderingContext = "getContext"
 
 /**
 Returns an object that exposes an API for drawing on the OffscreenCanvas object. contextId specifies the desired API: "2d", "bitmaprenderer", "webgl", or "webgl2". options is handled by that API.
@@ -128,11 +128,11 @@ Returns null if the canvas has already been initialized with another context typ
 [Read more on MDN](https://developer.mozilla.org/docs/Web/API/OffscreenCanvas/getContext)
 */
 @send
-external getContext3: (
+external getContext_WebGL2: (
   offscreenCanvas,
-  ~contextId: offscreenRenderingContextId,
-  ~options: JSON.t=?,
-) => webGLRenderingContext = "getContext"
+  @as("webgl2") _,
+  ~options: webGLContextAttributes=?,
+) => webGL2RenderingContext = "getContext"
 
 /**
 Returns an object that exposes an API for drawing on the OffscreenCanvas object. contextId specifies the desired API: "2d", "bitmaprenderer", "webgl", or "webgl2". options is handled by that API.
@@ -143,11 +143,11 @@ Returns null if the canvas has already been initialized with another context typ
 [Read more on MDN](https://developer.mozilla.org/docs/Web/API/OffscreenCanvas/getContext)
 */
 @send
-external getContext4: (
+external getContext_BitmapRenderer: (
   offscreenCanvas,
-  ~contextId: offscreenRenderingContextId,
-  ~options: JSON.t=?,
-) => webGL2RenderingContext = "getContext"
+  @as("bitmaprenderer") _,
+  ~options: imageBitmapRenderingContextSettings=?,
+) => imageBitmapRenderingContext = "getContext"
 
 /**
 Returns a newly created ImageBitmap object with the image in the OffscreenCanvas object. The image in the OffscreenCanvas object is replaced with a new blank image.