Key bindings customization

[0x2c7]

• Implement key binding customization with some built-in key combinations:

config.key_bindings = {
  RubyJard::Keys::CTRL_N        => 'jard filter switch',
  RubyJard::Keys::META_L        => 'list',
  RubyJard::Keys::CTRL_F1       => 'up',
  RubyJard::Keys::CTRL_SHIFT_F1 => 'down',
  RubyJard::Keys::META_D        => 'step',
  RubyJard::Keys::META_O  => 'step-out',
  RubyJard::Keys::CTRL_META_N   => 'next',
  RubyJard::Keys::META_F1       => 'continue',
  RubyJard::Keys::META_SHIFT_F1 => 'continue',
  RubyJard::Keys::CTRL_C        => 'interrupt'
}

• Increase the resilience of the key binding matcher. Key press spamming is easy now.
• Sync menu's action label to match customized key bindings.