Update charm codeowners

@fbetti @dmitzel I've tried to update this file - codeowners are the list of people who are automatically notified every time that the relative file is modified. Am I missing anybody?

@lpica @aanelli @cacochat please make sure that this file remains updated every time that new files are added or modifications are made

I expect some fixes to rates etc. to be made in the next months and affected people should be automatically made aware of this