I believe Chrome Add-ons means a Browser Extension..
(Talking about how you can do with AI)
If yes, install any IDE (VS Code etc)..
Enter the prompt, like you are a complete noob, wanna build an extension like this this.
Ask repetitively wherever you are confuse.. and you are good to go!
Creating a very basic Chrome extension is fairly simple.. you will be able to create and start an extension within 30 mins.. now comes the whole deal - What you want your extension to do? Depending upon that it will take time..
Usually for dev extension.. if you don't wanna store any info.. you don't need any DB, if you wanna store.. Browser's does provide storage options.. although I'm quite skeptical about them.. cz they might slow down Browser.. but yeah they provide sufficient space tho..
All these MySQL & stuffs comes into the picture if you wanna store information somewhere else.. but then it involves a lot of other things, like connection to this "somewhere else", hosting it.. writing code to talk to this DB/ Backend.. etc etc..
I'll suggest start creating a basic extension..fairly simple with little or no storage requirements..