Enhancement: Add default case handling in generated pbjs output

[saurabh-pingale]

This PR introduces enhancements to the protobuf-generated files by adding a default case handling mechanism in the generated pbjs code.

Enhancement: #1106

Changes Introduced

• Added default case in the generated header section to handle unexpected enum values.
• Ensures safer parsing and avoids runtime issues when new/unknown values are encountered.

Screenshots & References

1. Proto file used for testing (test.proto)

2. Command used to generate pbjs file

pbjs -t static-module -w commonjs -o test.js test.proto

3. Generated file showing default case in header