Add SaveImageWEBP Node for Saving Images in WebP Format

[TechnoByteJS]

This pull request introduces a new node, SaveImageWEBP, which allows users to save images in the WebP format. As WebP images are typically 25-35% smaller than PNGs with comparable quality.

This node:

• Works exactly like the SaveImage node, but saves in WebP instead of PNG.
• Lets users choose between lossless and lossy compression, adjust quality levels, and select encoding methods (default, fastest, or slowest).
• Supports embedding metadata (e.g., prompts and additional info) into the WebP files using Exif tags, and is compatible with ComfyUI's existing metadata system. Metadata handling uses Exif tags, just like the SaveAnimatedWEBP node.