[GSoC] A late proposal: a modern send-email

I know it's tooo late to post proposal here, but I'd like to let my idea known by others.

# Summary Although many projects hosted on github or gitlab adopt the fork-and-merge working flow, email is still irreplaceable for its compatibility. However, the send-email module is old and difficult for new users. I’d like to improve it and implement a more modern interface for git-send-email.

# Purpose
The current implementation of send-email is based on perl and has only
a tui, it has two problems:
- user must install a ton of dependencies before submit a single patch.
- tui and parameter are both not quite friendly to new users.

# Plan
So I propose to implement following:
- Allow user to send mail via a [`mailto`
link](https://en.wikipedia.org/wiki/Mailto). so that users could
complete the mail in their favorite email clients such as gmail, mutt,
alpine and even gmail for android through
[termux](https://termux.com/) (termux is a terminal emulator on
Android and has an API to call android system to open a link).
- Build a simple email client (maybe a web components based web app or
wxwidgets based GUI client, they are both cross-platform) which is
easy to use for sending patch without disrupting the mailbox format.

Here is my proposal:

https://docs.google.com/document/d/1PbaKJOUWjpAh0JEunqhKWiWW4SAr_-7DH_ss4WkgDGs/edit