Better Err message when $TERM not found

[cattyman919]

PR Description

Issue

The setupterm function returns an vague error message of exit status 1 when $TERM variable is set to an invalid value.

> export TERM=skibidi
> infocmp: couldn't open terminfo file /usr/share/terminfo/s/skibidi.

This will return `exit status 1` in from the go program

tcell/terminfo/dynamic/dynamic.go

Lines 119 to 130 in 340fa4f

	func (tc *termcap) setupterm(name string) error {
	cmd := exec.Command("infocmp", "-1", name)
	output := &bytes.Buffer{}
	cmd.Stdout = output
	tc.strs = make(map[string]string)
	tc.bools = make(map[string]bool)
	tc.nums = make(map[string]int)
	if err := cmd.Run(); err != nil {
	return err
	}

The error returns 'exit status 1' which is a vague error message to the user

Related Issue & PR

Trying to resolve jesseduffield/lazygit#4868
Related pull Request jesseduffield/lazygit#4881 (comment)