UI / UX improvements

[thisisjoshford]

This PR makes several UI/UX improvements for this example.

• Improved styling and formatting
• Moved derived address & balance closer to input fields
• Adds sepolia gas prices (testnet price spiked within past month and caused failures)

Before:

After:

[gagdiez]

I like some changes, others I feel that are not necessary.

I like:

• Showing the GAS
• Being more explicit about the chain and address being derived

I don't feel they are needed:

• Adding dark mode
• Changing how the layout / form looks

[gagdiez]

I don't feel that we need to add dark mode or change how the layout / form looks

[thisisjoshford]

I don't feel that we need to add dark mode or change how the layout / form looks

Ok, I switched it back to light mode, but I do feel that this form looks more polished/professional no?