LibWeb: Add Canvas Context2D basic text align and text baseline support

Add the CanvasTextDrawingStyles mixin with the textAlign and
textBaseline attributes. Update fill_text in CanvasRenderingContext2D
to move the text rect by the text align and text baseline attributes.
Wrote a simple HTML example to showcase the new features.

Userland/Libraries/LibWeb/Forward.h

@@ -36,6 +36,8 @@ class OptionConstructor;
 enum class AudioContextLatencyCategory;
 enum class CanPlayTypeResult;
 enum class CanvasFillRule;
+enum class CanvasTextAlign;
+enum class CanvasTextBaseline;
 enum class DOMParserSupportedType;
 enum class EndingType;
 enum class ImageSmoothingQuality;