WebGL2: Use UNPACK_ALIGNMENT of 1

Fixes issues when uploading one or two-channel textures.

src/gfx/platform/GfxPlatformWebGL2.ts

@@ -566,6 +566,7 @@ class GfxImplP_GL implements GfxSwapChain, GfxDevice {
         // We always have depth & stencil test enabled.
         gl.enable(gl.DEPTH_TEST);
         gl.enable(gl.STENCIL_TEST);
+        gl.pixelStorei(gl.UNPACK_ALIGNMENT, 1);
 
         this._checkLimits();
         this._checkForBugQuirks();