feat: add ChatGPT support

[baruchiro]

• move finder code to share with all content
• rename indicator.js -> create-element.js
• move element creation to create-element
• inject contentElementSelector
• include the self element in findRanges
• add the content.chatgpt to build

Part of #86

Need help with the style:

[GuyNachshon]

it seems like we have two options to solve this:

1. diverge the CSS when we are on chatgpt's URL to manipulate the color
2. add a more comprehended solution traversing up to the first background colour and determining the colour based on it.

@baruchiro @jossef WDYT?

[baruchiro]

On Hold: Waiting for @jossef to finish the Figma styles and support dark mode.