Como adicionar o Git-Bash no Windows Terminal

 This is the complete answer (GitBash + color scheme + icon + context menu)

1) Set default profile:

"globals" : 
{
    "defaultProfile" : "{00000000-0000-0000-0000-000000000001}",
    ...

2) Add GitBash profile

"profiles" : 
[
    {
        "guid": "{00000000-0000-0000-0000-000000000001}",
        "acrylicOpacity" : 0.75,
        "closeOnExit" : true,
        "colorScheme" : "GitBash",
        "commandline" : "\"%PROGRAMFILES%\\Git\\usr\\bin\\bash.exe\" --login -i -l",
        "cursorColor" : "#FFFFFF",
        "cursorShape" : "bar",
        "fontFace" : "Consolas",
        "fontSize" : 10,
        "historySize" : 9001,
        "icon" : "%PROGRAMFILES%\\Git\\mingw64\\share\\git\\git-for-windows.ico", 
        "name" : "GitBash",
        "padding" : "0, 0, 0, 0",
        "snapOnInput" : true,
        "startingDirectory" : "%USERPROFILE%",
        "useAcrylic" : false        
    },

3) Add GitBash color scheme

"schemes" : 
[
    {
        "background" : "#000000",
        "black" : "#0C0C0C",
        "blue" : "#6060ff",
        "brightBlack" : "#767676",
        "brightBlue" : "#3B78FF",
        "brightCyan" : "#61D6D6",
        "brightGreen" : "#16C60C",
        "brightPurple" : "#B4009E",
        "brightRed" : "#E74856",
        "brightWhite" : "#F2F2F2",
        "brightYellow" : "#F9F1A5",
        "cyan" : "#3A96DD",
        "foreground" : "#bfbfbf",
        "green" : "#00a400",
        "name" : "GitBash",
        "purple" : "#bf00bf",
        "red" : "#bf0000",
        "white" : "#ffffff",
        "yellow" : "#bfbf00",
        "grey" : "#bfbfbf"
    },  

4) To add a right-click context menu "Windows Terminal Here"

Windows Registry Editor Version 5.00

[HKEY_CLASSES_ROOT\Directory\Background\shell\wt]
@="Windows terminal here"
"Icon"="C:\\Users\\{YOUR_WINDOWS_USERNAME}\\AppData\\Local\\Microsoft\\WindowsApps\\{YOUR_ICONS_FOLDER}\\icon.ico"

[HKEY_CLASSES_ROOT\Directory\Background\shell\wt\command]
@="\"C:\\Users\\{YOUR_WINDOWS_USERNAME}\\AppData\\Local\\Microsoft\\WindowsApps\\wt.exe\""

• replace {YOUR_WINDOWS_USERNAME}
• create icon folder, put the icon there and replace {YOUR_ICONS_FOLDER}
• save this in a whatever_filename.reg file and run it.