isValid static method
Checks if the string input
is a valid LRC using Regex.
Implementation
static bool isValid(String input) => RegExp(
r'^([\r\n]*\[((ti)|(a[rlu])|(by)|([rv]e)|(length)|(offset)|(la)):.+\][\r\n]*)*([\r\n]*\[\d\d:\d\d\.\d\d\].*){2,}[\r\n]*$')
.hasMatch(input.trim());