fix: small comment, error string, and guard cleanups (addons only)

Co-authored-by: Daniel Imms <Tyriar@users.noreply.github.com>

addons/addon-serialize/src/SerializeAddon.ts

@@ -173,7 +173,7 @@ class StringSerializeHandler extends BaseSerializeHandler {
   private _thisRowLastSecondChar: IBufferCell = this._buffer.getNullCell();
   private _nextRowFirstChar: IBufferCell = this._buffer.getNullCell();
   protected _rowEnd(row: number, isLastRow: boolean): void {
-    // if there is colorful empty cell at line end, whe must pad it back, or the the color block
+    // if there is colorful empty cell at line end, we must pad it back, or the color block
     // will missing
     if (this._nullCellCount > 0 && !equalBg(this._cursorStyle, this._backgroundCell)) {
       // use clear right to set background.

addons/addon-webgl/src/TextureAtlas.ts

@@ -1125,7 +1125,7 @@ function clearColor(imageData: ImageData, bg: IColor, fg: IColor, enableThreshol
   // were covered (fg=#8ae234, bg=#c4a000).
   const threshold = Math.floor((Math.abs(r - fgR) + Math.abs(g - fgG) + Math.abs(b - fgB)) / 12);
 
-  // Set alpha channel of relevent pixels to 0
+  // Set alpha channel of relevant pixels to 0
   let isEmpty = true;
   for (let offset = 0; offset < imageData.data.length; offset += 4) {
     // Check exact match

addons/addon-webgl/src/WebglAddon.ts

@@ -40,7 +40,7 @@ export class WebglAddon extends Disposable implements ITerminalAddon, IWebglApi
       };
       const gl = document.createElement('canvas').getContext('webgl2', contextAttributes) as IWebGL2RenderingContext;
       if (!gl) {
-        throw new Error('Webgl2 is only supported on Safari 16 and above');
+        throw new Error('WebGL2 is only supported on Safari 16 and above');
       }
     }
     super();