Backspace deletes last readonly character

[suleyman-shb]

Steps to reproduct:
Start new "ConsoleControlSample.WPF" process.
Click "Run command" starts new command shell
Hit backspace on input area
Last character on output, probable a ">" character is removed.

Fix proposal:
on "richTextBoxConsole_PreviewKeyDown" method, change

var caretPosition = richTextBoxConsole.GetCaretPosition();
var delta = caretPosition - inputStartPos;
var inReadOnlyZone = delta < 0;

with this

var caretPosition = richTextBoxConsole.GetCaretPosition();
var delta = caretPosition - inputStartPos;
var inReadOnlyZone = delta <= 0;