Add svg linter and fix incorrect svgs (#30086)

Fixes https://github.com/go-gitea/gitea/issues/30082.

Adds a new linter that searches for non-existant SVG images in
templates. Output before the fix was:

```
$ make lint-templates
SVG "octicon-warning" not found, used in templates/devtest/flex-list.tmpl
SVG "octicon-warning" not found, used in templates/devtest/flex-list.tmpl
SVG "octicon-markup" not found, used in templates/repo/diff/comment_form.tmpl
make: *** [Makefile:438: lint-templates] Error 1
```

<img width="306" alt="Screenshot 2024-03-25 at 23 31 05"
src="https://github.com/go-gitea/gitea/assets/115237/1052d1a9-bfec-4d5a-9cae-f895f78f7c93">

.github/workflows/files-changed.yml

@@ -73,6 +73,7 @@ jobs:
               - "Makefile"
 
             templates:
+              - "tools/lint-templates-*.js"
               - "templates/**/*.tmpl"
               - "pyproject.toml"
               - "poetry.lock"

.github/workflows/pull-compliance.yml

@@ -35,8 +35,12 @@ jobs:
       - uses: actions/setup-python@v5
         with:
           python-version: "3.12"
+      - uses: actions/setup-node@v4
+        with:
+          node-version: 20
       - run: pip install poetry
       - run: make deps-py
+      - run: make deps-frontend
       - run: make lint-templates
 
   lint-yaml: