Add tasks for all the new languages

Task/Longest-common-subsequence/Egison/longest-common-subsequence-1.egison

@@ -0,0 +1,8 @@
+(define $common-seqs
+  (lambda [$xs $ys]
+    (match-all [xs ys] [(list char) (list char)]
+      [[(loop $i [1 $n] <join _ <cons $c_i ...>> _)
+        (loop $i [1 ,n] <join _ <cons ,c_i ...>> _)]
+       (map (lambda [$i] c_i) (between 1 n))])))
+
+(define $lcs (compose common-seqs rac))

Task/Longest-common-subsequence/Egison/longest-common-subsequence-2.egison

@@ -0,0 +1,2 @@
+> (lcs "thisisatest" "testing123testing"))
+"tsitest"