Add tasks for all the new languages

Task/Fast-Fourier-transform/Sidef/fast-fourier-transform.sidef

@@ -0,0 +1,16 @@
+func fft(arr) {
+    arr.len == 1 && return arr
+
+    var evn = fft([arr[^arr -> grep { .is_even }]])
+    var odd = fft([arr[^arr -> grep { .is_odd  }]])
+    var twd = (Num.tau.i / arr.len)
+
+    ^odd -> map {|n| odd[n] *= ::exp(twd * n)}
+    (evn »+« odd) + (evn »-« odd)
+}
+
+var cycles = 3
+var sequence = 0..15
+var wave = sequence.map {|n| ::sin(n * Num.tau / sequence.len * cycles) }
+say "wave:#{wave.map{|w| '%6.3f' % w }.join(' ')}"
+say "fft: #{fft(wave).map { '%6.3f' % .abs }.join(' ')}"