create an simple JFrame with no content in it

but had set the frame title to "Little Typer"
add main frame to the main function(LittleTyper.java)
design the starting panel,  two button in it

button 1 :  Single player mode
button 2 :  Network battle mode
add cardLayout to MainFrame, and add StartPanel into it
simply design the Difficulty panel
simply design the "HostOrClient" Panel, add 2 buttons in it

button1 : Host a game
button2 : Be a client
Revert "simply design the "HostOrClient" Panel, add 2 buttons in it"

This reverts commit 8a367c62ad44b32b82e9cbd0d79dbc781176777b.
Revert "simply design the Difficulty panel"

This reverts commit 2cf6edce3ec271df91ecc7a2fb7fd3be9551121a.
simply design DifficultyPanel, add a label

label says : "Please choose a difficulty"