Enable JSON schema validator support for "format" keyword

Support for the JSON schema "format" keyword was moved to a separate package in ajv v7.0.0 (ajv-cli v4.0.0). If this package is not
installed and specified as a module via the ajv-cli command, validation against any schema that uses "format" fails, even
when the instance document is completely valid. Even though the JSON schema currently in use does not have a "format"
keyword, there's no reason one couldn't be added at any moment, so it's safest to just add support now.

The change to ajv was done for security purposes when used with untrusted data, which is not a concern here.

Author: per1234

.github/workflows/check-taskfiles.yml

@@ -42,13 +42,18 @@ jobs:
           location: ${{ runner.temp }}/taskfile-schema
 
       - name: Install JSON schema validator
-        run: sudo npm install --global ajv-cli
+        run: |
+          sudo npm install \
+            --global \
+            ajv-cli \
+            ajv-formats
 
       - name: Validate ${{ matrix.file }}
         run: |
           # See: https://github.com/ajv-validator/ajv-cli#readme
           ajv validate \
             --all-errors \
             --strict=false \
+            -c ajv-formats \
             -s "${{ steps.download-schema.outputs.file-path }}" \
             -d "${{ matrix.file }}"