Arithmetic overflow occurs while using API LineRange::from()

[HeeillWang]

What steps will reproduce the bug?
I executed fuzz testing with bat public APIs and found crash case.

let fuzz_arg1 = "18446744073709551615:+1";
LineRange::from(fuzz_arg1);

What happens?

Thread '<unnamed>' panicked at 'attempt to add with overflow', /rustc/871b5952023139738f72eba235063575062bc2e9/library/core/src/ops/arith.rs:109

The overflow occurs with this statement :

bat/src/line_range.rs

Line 56 in 5a240f3

new_range.lower + more_lines

What did you expect to happen instead?
Need assertion to prevent arith overflow, or need to explicitly mention panic condition.

[sohang3112]

Maybe saturating_add(new_range.lower, more_lines) can be done here to avoid panicking.

[HeeillWang]

Maybe saturating_add(new_range.lower, more_lines) can be done here to avoid panicking.

Looks nice, better than assert!.