Add Capitalize in Elvish (#4305)

Author: Kaamkiya

archive/e/elvish/capitalize.elv

@@ -0,0 +1,18 @@
+use str
+
+fn die {
+  echo 'Usage: please provide a string'
+  exit 1
+}
+
+if (> 1 (count $args)) {
+  die
+}
+
+var s = $args[0]
+
+if (> 1 (count $s)) {
+  die
+}
+
+echo (str:join '' [(str:to-upper $s[0]) $s[1..]])