feat: Implement a simple onboarding flow for new users

[dineshsutihar]

Is your feature request related to a problem?

When a user first installs the extension, they receive no guidance on how to use it. They might not discover the keyboard shortcut or understand the element picker workflow, leading to confusion and a poor first-time experience.

Describe the solution you'd like

1. Create a simple, clean welcome.html page within the extension.

2. Use the chrome.runtime.onInstalled event listener in the background script. When the event reason is "install", open the welcome.html page in a new tab.

3. The welcome page should clearly and concisely explain the 3-step process for using the extension, perhaps with small GIFs or images:

Step 1: Use the keyboard shortcut to activate the code picker.

Step 2: Click on any code block on a webpage.

Step 3: View the translation in the injected UI.

Additional context

A clear onboarding process is critical for user retention. It ensures users understand the extension's core functionality and have a successful first interaction, which makes them much more likely to continue using the tool.

[whatsupsumit]

i can get this done !!
assign me this one
would like to work on it
@dineshsutihar

[Chesblaw]

@dineshsutihar can i work on this

[dineshsutihar]

Thanks for volunteering to work on this! Everyone is welcome to submit a PR. We'll evaluate all submissions and merge the one that best solves the issue.