Add tasks for all the new languages

Task/History-variables/EchoLisp/history-variables.echolisp

@@ -0,0 +1,22 @@
+(define-syntax-rule (make-h-var name) (define name (stack (gensym))))
+(define-syntax-rule (h-get name) (stack-top name))
+(define-syntax-rule (h-set name value) (push name value))
+(define-syntax-rule (h-undo name)
+	(begin
+	(pop name)
+	(when ( stack-empty? name) (error "no more values" 'name))
+	(stack-top name)))
+						
+(define-syntax-rule (h-values name) (stack->list name))
+;; usage
+(make-h-var x)→ x
+
+(h-set x 42) → 42
+(h-set x 666)→ 666
+(h-set x 'elvis)→ elvis
+(h-values x) → (42 666 elvis) ;; historized values
+
+(h-get x) → elvis
+(h-undo x)→ 666
+(h-undo x) → 42
+(h-undo x) → ❌ error: no more values x