Re-add the ability to view or edit the latest zet

Signed-off-by: Oliver Davies <oliver@oliverdavies.uk>

internal/lib/zet.go

@@ -82,6 +82,12 @@ func GetAllZets() []int {
 	return sorted
 }
 
+func GetLatestZet() int {
+	z := GetAllZets()
+
+	return z[len(z)-1]
+}
+
 func SearchZets(query string) []int {
 	zets, err := execGitCommand("grep", "-i", "--name-only", "--word-regex", query)