feat: implement client start/stop commands

- add ClientCommand struct to handle incoming commands
- introduce timerStopChannel to manage timer stopping
- modify startTimer to return a boolean for success/failure
- update runPomodoroTimer to handle timer start/stop commands
- add start and stop buttons in the index.html for user interaction

🤖

README.md

@@ -2,6 +2,10 @@
 
 A pomodoro server
 
+## Installation
+
+`go install git.smsvc.net/pomodoro/GoTomato@latest`
+
 ## Testing
 
 ```