Adding Webp Support

[Foxy-null]

Description

Adding Webp Support

This fixes #140

What I did

• Updated _vendor/imageresize.py to latest one (MIT License)
• Added "Webp" to SUPPORTED_BITMAP_FORMATS in ./consts.py

Checklist:

Please replace the space inside the brackets with an x and fill out the ellipses if the following items apply:

• [x] I've read and understood the contribution guidelines
• [x] I've tested my changes against at least one of the following Anki builds:
  • [x] Latest standard Anki 2.1 binary build
  • Latest alternative Anki 2.1 binary build
• [x] I've tested my changes on at least one of the following platforms:
  • Linux, version:
  • [x] Windows, version: Windows 10 Pro Build 19045.3208
  • macOS, version:
• My changes potentially affect non-desktop platforms, of which I've tested:
  • AnkiMobile, version:
  • AnkiDroid, version:
  • AnkiWeb