Send BTN_LEFT with sendkey for mouse buttons

[iberianpig]

Overview

This pull request adds mouse button operations to the sendkey command. With this change, operating mouse buttons will be similar to operating keyboard keys.

Details of Changes

• Mouse button operations (e.g., BTN_LEFT, BTN_RIGHT, BTN_MIDDLE) have been added to fusuma-sendkey.
• The functionalities in the Keyboard class have been extended to handle mouse button operations.
• Test cases for keyboard and mouse button operations have been added.

Notes

• Mouse button operations are available only when mouse buttons are implemented on the keyboard.
• Available mouse buttons can be checked with the command fusuma-sendkey -l | grep BTN_.
• A virtual keyboard using uinput (e.g., fusuma-plugin-remap) will likely be needed.

Usage Example

It is important to note that you need to specify the mouse button with the prefix BTN_ as shown below.

---
context:
  thumbsense: true

remap:
  F: BTN_LEFT # <- remaps to left click using fusuma-plugin-remap
              # fusuma-plugin-remap already supports mouse button operations.

  E: 
    sendkey: LEFTCTRL+BTN_LEFT # <- sends left click with left control key using fusuma-plugin-sendkey
                               # This PR adds mouse button operations to the `sendkey` command.

In command line, following command can be executed to test the feature.

$ fusuma-sendkey BTN_RIGHT

$ fusuma-sendkey -l | grep -i BTN_
BTN_0
BTN_1
BTN_2
BTN_3
BTN_4
BTN_5
BTN_6
BTN_7
BTN_8
BTN_9
BTN_LEFT
BTN_RIGHT
BTN_MIDDLE
BTN_SIDE
BTN_EXTRA
BTN_FORWARD
BTN_BACK
BTN_TASK