Update readme

[irina-baeva]

The purpose of the PR is to update the README with up-to-date information regarding the project local installation.

[jmcodingde]

Those additions to the readme are helpful for our internal development, thank you for adding them @irina-baeva !

We have to keep in mind that this repo is public on GitHub and it also pushes the public npm package @getsupertab/supertab-browser.

The readme is published on npm as is and in that context we're addressing external developers. For them, bun is not a requirement and they are probably mostly interested in how to install the package as a dependency and how to use it rather than how to contribute.

Maybe we could put those (internal) development instructions into a separate section and focus on the external developer audience in the rest of the readme

[jmcodingde]

If we want to trigger a version bump and create a new release, the PR title (i.e. the final commit message title after squashing) has to conform to the semantic commit message format.