Drop composer.lock and ignore it for library repo

composer.lock is not appropriate for libraries as it is ignored by
consumers and gives a false sense of reproducibility.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: aymanrb

.gitignore

@@ -17,6 +17,7 @@ local.properties
 *.tar
 *.zip
 vendor/
+composer.lock
 
 # Logs and databases #
 ######################