Mark parser.c and Parser.java as generated files

This way they're hidden in diffs.

However so ensure no code is slipped into it, we ensure on CI
that what was committed is really the Ragel output.

.gitattributes

@@ -0,0 +1,2 @@
+ext/json/ext/parser/parser.c linguist-generated=true
+java/src/json/ext/Parser.java linguist-generated=true

.github/workflows/ci.yml

@@ -50,6 +50,17 @@ jobs:
 
       - run: rake compile
 
+      - run: |
+        if ! git diff-index --quiet HEAD; then
+          printf 'These files changed when running the command:\n\n'
+
+          git diff --name-only | while read -r n ; do
+            echo "* $n"
+          done
+
+          exit 1
+        fi
+
       - run: rake test JSON_COMPACT=1
 
       - run: rake build