I need to include some css and js files into my kibana plugin. I have tried adding the "files" option (explicit path without using wildcards) to package.json and run "yarn build ...". However, I can't see any file size change in the output "build" directory.
I have also tried adding the files to "include" config in tsconfig.json and still no luck.
As for extra dependency, you can install as many packages from npm as you like. But probably they should be included in your plugin's archive because Kibana doesn't install them when your plugin is installed. At least it was a case few years back.