pre-commit: Exclude all image files from trailing whitespace checks

Previously we excluded SVG files from these checks with a regex matching
SVG filenames.

I learnt that pre-commit uses the “identify” library to determine a set
of types for a file. This library already knows that `.svg` files are
images:

    $ identify-cli addons/git_describe/label/icon.svg
    ["file", "image", "non-executable", "svg", "text", "xml"]

SVG is not the only text-based image format. We don't want to run
whitespace checks on any kind of image file.

Exclude image files by type, not SVGs by filename.

https://pypi.org/project/identify/

Author: wjt

.pre-commit-config.yaml

@@ -14,9 +14,9 @@ repos:
   - id: check-illegal-windows-names
   - id: check-yaml
   - id: end-of-file-fixer
-    exclude: \.svg$
+    exclude_types: [image]
   - id: trailing-whitespace
-    exclude: \.svg$
+    exclude_types: [image]
 
 - repo: https://github.com/editorconfig-checker/editorconfig-checker
   rev: v3.4.0