Add Common Use Cases, User Onboarding, Permissions Explanation, and Troubleshooting to README

[gustavogabaldon]

The PR enhances the Dismoi README by adding various sections that improve both the user and developer experience:

Common Use Cases: Provides practical examples of how Dismoi can be used for fact-checking, product reviews, collaborative research, and news commentary. User Onboarding Guide: Step-by-step instructions for new users on how to install the extension, create an account, and start following informers. Permissions Explained: A simple breakdown of the permissions required by Dismoi, explaining their purpose and ensuring transparency for users. Troubleshooting Guide: Solutions to common issues, such as extension loading errors, permission request popups, and missing informer comments.

These additions aim to make Dismoi more accessible to new users and developers, so it is then a smoother experience while using or contributing to the project.