Add tasks for all the new languages

Task/Run-length-encoding/Sidef/run-length-encoding-1.sidef

@@ -0,0 +1,7 @@
+func encode(str) {
+  str.gsub(/((.)(\2*))/, {|a,b| "#{a.len}#{b}" });
+}
+
+func decode(str) {
+  str.gsub(/(\d+)(.)/, {|a,b| b * a.to_i });
+}

Task/Run-length-encoding/Sidef/run-length-encoding-2.sidef

@@ -0,0 +1,12 @@
+func encode(str) {
+    str.gsub(/(.)(\1{0,254})/, {|a,b| b.len+1 -> chr + a});
+}
+
+func decode(str) {
+     var chars = str.chars;
+     var r = '';
+     (chars.len/2 -> int).range.each { |i|
+         r += (chars[2*i + 1] * chars[2*i].ord);
+     }
+     return r;
+}