Add tasks for all the new languages

Task/Substring/Phix/substring-1.phix

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+--(1) starting from n characters in and of m length;
+--(2) starting from n characters in, up to the end of the string;
+--(3) whole string minus last character;
+--(4) starting from a known character within the string and of m length;
+--(5) starting from a known substring within the string and of m length.
+
+constant sentence = "the last thing the man said was the",
+         n = 10, m = 5
+integer k, l
+l = n+m-1
+if l<=length(sentence) then
+    ?sentence[n..l]           -- (1)
+end if
+if n<=length(sentence) then
+    ?sentence[n..-1]          -- (2) or [n..$]
+end if
+if length(sentence)>0 then
+    ?sentence[1..-2]          -- (3) or [1..$-1]
+end if
+k = find('m',sentence)
+l = k+m-1
+if l<=length(sentence) then
+    ?sentence[k..l]           -- (4)
+end if
+k = match("aid",sentence)
+l = k+m-1
+if l<=length(sentence) then
+    ?sentence[k..l]           -- (5)
+end if

Task/Substring/Phix/substring-2.phix

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+?sentence[n..n+m-1]
+?sentence[n..-1]
+?sentence[1..-2]
+?(sentence[find('m',sentence)..$])[1..m]
+?(sentence[match("aid",sentence)..$])[1..m]