Add tasks for all the new languages

Task/Collections/Sidef/collections-1.sidef

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+# creating an empty array and adding values
+var a = []          #=> []
+a[0] = 1            #=> [1]
+a[3] = "abc"        #=> [1, nil, nil, "abc"]
+a << 3.14           #=> [1, nil, nil, "abc", 3.14]

Task/Collections/Sidef/collections-2.sidef

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+# creating an empty hash
+var h = Hash()    #=> Hash()
+h{:foo} = 1       #=> Hash("foo"=>1)
+h{:bar} = 2.4     #=> Hash("foo"=>1, "bar"=>2.4)
+h{:bar} += 3      #=> Hash("foo"=>1, "bar"=>5.4)

Task/Collections/Sidef/collections-3.sidef

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+# create a simple pair
+var p = Pair('a', 'b')
+say p.first;            #=> 'a'
+say p.second;           #=> 'b'
+
+# create a pair of pairs
+var pair = 'foo':'bar':'baz':();   # => Pair('foo', Pair('bar', Pair('baz', nil)))
+
+# iterate over the values of a pair of pairs
+loop {
+    say pair.first;                #=> 'foo', 'bar', 'baz'
+    pair = pair.second;
+    pair == nil && break;
+}

Task/Collections/Sidef/collections-4.sidef

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+# creating a struct
+struct Person {
+    String name,
+    Number age,
+    String sex
+}
+
+var a = Person("John Smith", 41, :man)
+
+a.age += 1                  # increment age
+a.name = "Dr. #{a.name}"    # update name
+
+say a.name          #=> "Dr. John Smith"
+say a.age           #=> 42
+say a.sex           #=> "man"