update readme

Author: xtyxtyx

README.md

@@ -1,6 +1,6 @@
 ## Terminal Lite
 
-Experimental terminal emulator application written in Flutter.
+Experimental cross-platform terminal emulator application written in Flutter.
 
 ## Screenshots
 
@@ -31,8 +31,22 @@ Experimental terminal emulator application written in Flutter.
 
 ## Build
 
+**Flutter 1.22.0+ is recommended to build Terminal Lite.**
+
 ```
-flutter packages get
-flutter packages upgrade
+flutter pub get
+flutter pub upgrade
 flutter run --release
-```
+```
+
+## Known Issues
+
+- [Pty](https://github.com/TerminalStudio/pty) may not work in **debug mode**.
+- Some special characters may not render in **MacOS**, maybe caused by [fontFamilyFallback](https://github.com/TerminalStudio/xterm.dart/blob/2800cfba0e1a945b3588e5658cf0801684c91027/lib/theme/terminal_style.dart#L2)?
+- When multiple tabs are opened, focus may not move between those tabs correctly.
+
+## Features and bugs
+
+Please file feature requests and bugs at the [issue tracker](https://github.com/TerminalStudio/lite/issues).
+
+Contributions are always welcome!