Add a better layout and theme for the message list so it's more ergonomic

Comments/Description:

This is to close #8 (closed) issue. The new interface is much more "material" and ergonomic. The subject of the email is shown first (instead of the sender). The sender is displayed (either compact or with full address) below. Then, a quick & small email summary is shown. The thread message count is only displayed if there is more than a single message.

I'm using light font here, and the same color for both unread & read messages. Unread messages are using bold font.

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Important

• Added description to PR
• Linked issue ticket(s) to PR
• Passing the lint
• I read the contributing section and agree to them
• I agree to the license

Addresses issue(s):

• Ticket: #8 (closed)

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