Add tasks for all the new languages

Task/Substring-Top-and-tail/Eero/substring-top-and-tail.eero

@@ -0,0 +1,18 @@
+#import <Foundation/Foundation.h>
+
+int main()
+  autoreleasepool
+
+    s := 'knight'
+    Log( '%@', s[1 .. s.length-1] )  // strip first character
+
+    s = 'socks'
+    Log( '%@', s[0 .. s.length-2] )  // strip last character
+
+    s = 'brooms'
+    Log( '%@', s[1 .. s.length-2] )  // strip both first and last characters
+
+    s = 'Δημοτική'
+    Log( '%@', s[1 .. s.length-2] )  // strip both first and last characters
+
+  return 0