Give powershell its own scheme (#2936)

Fixes #2883.

src/cascadia/TerminalApp/defaults.json

@@ -17,9 +17,8 @@
             "commandline": "powershell.exe",
             "hidden": false,
             "startingDirectory": "%USERPROFILE%",
-            "background": "#012456",
             "closeOnExit": true,
-            "colorScheme": "Campbell",
+            "colorScheme": "Campbell Powershell",
             "cursorColor": "#FFFFFF",
             "cursorShape": "bar",
             "fontFace": "Consolas",
@@ -73,6 +72,27 @@
             "brightCyan": "#61D6D6",
             "brightWhite": "#F2F2F2"
         },
+        {
+            "name": "Campbell Powershell",
+            "foreground": "#CCCCCC",
+            "background": "#012456",
+            "black": "#0C0C0C",
+            "red": "#C50F1F",
+            "green": "#13A10E",
+            "yellow": "#C19C00",
+            "blue": "#0037DA",
+            "purple": "#881798",
+            "cyan": "#3A96DD",
+            "white": "#CCCCCC",
+            "brightBlack": "#767676",
+            "brightRed": "#E74856",
+            "brightGreen": "#16C60C",
+            "brightYellow": "#F9F1A5",
+            "brightBlue": "#3B78FF",
+            "brightPurple": "#B4009E",
+            "brightCyan": "#61D6D6",
+            "brightWhite": "#F2F2F2"
+        },
         {
             "name": "Vintage",
             "foreground": "#C0C0C0",