Add file format versioning

Author: jaydeluca

docs/instrumentation-list.yaml

@@ -2,6 +2,8 @@
 # The structure and contents are a work in progress and subject to change.
 # For more information see: https://github.com/open-telemetry/opentelemetry-java-instrumentation/issues/13468
 
+file_format: 0.1
+
 libraries:
   activej:
   - name: activej-http-6.0

instrumentation-docs/src/main/java/io/opentelemetry/instrumentation/docs/DocGeneratorApplication.java

@@ -43,6 +43,7 @@ public static void main(String[] args) throws IOException {
       writer.write("# The structure and contents are a work in progress and subject to change.\n");
       writer.write(
           "# For more information see: https://github.com/open-telemetry/opentelemetry-java-instrumentation/issues/13468\n\n");
+      writer.write("file_format: 0.1\n\n");
       YamlHelper.generateInstrumentationYaml(modules, writer);
     }