chore: use go fix to enhance codebase (#29)

This pull request modernizes the codebase by adopting Go 1.21+ features, including built-in functions like min and max, standard library iterators such as strings.SplitSeq and strings.FieldsSeq, utility functions like maps.Copy and slices.Contains, and string manipulation helpers like strings.Cut and strings.CutPrefix. Feedback is provided on a test file where the usage of strings.Builder can be further optimized to avoid unnecessary string allocations during concatenation.

`go fix -diff ./...`

commands/git/git.go

@@ -34,7 +34,7 @@ func GitCommitGenerator(tokens []string, _ string, _ string) []core.Suggestion {
 	}
 
 	var results []core.Suggestion
-	for _, line := range strings.Split(string(out), "\n") {
+	for line := range strings.SplitSeq(string(out), "\n") {
 		line = strings.TrimSpace(line)
 		if line == "" {
 			continue