Add tasks for all the new languages

Task/Regular-expressions/Sidef/regular-expressions-1.sidef

@@ -0,0 +1,4 @@
+var str = "I am a string";
+if (str =~ /string$/) {
+    print "Ends with 'string'\n";
+}

Task/Regular-expressions/Sidef/regular-expressions-2.sidef

@@ -0,0 +1,8 @@
+var str = <<'EOF';
+    x:Foo
+    y:Bar
+EOF
+
+while (var m = str=~/(\w+):(\S+)/g) {
+    say "#{m[0]} -> #{m[1]}";
+}

Task/Regular-expressions/Sidef/regular-expressions-3.sidef

@@ -0,0 +1,12 @@
+var str = "I am a string";
+
+# Substitute something mached by a regex
+str.sub!(/ a /, ' another ');   # "I am a string" => "I am another string"
+
+# Remove something matched by a regex
+str -= / \Kanother /i;          # "I am another string" => "I am string"
+
+# Global subtitution with a block
+str = str.gsub(/(\w+)/, {|s1| 'x' * s1.len});  # globaly replace any word with 'xxx'
+
+say str;     # prints: 'x xx xxxxxx'