doc: sample: add match-statement syntax and ir samples

doc/sample/Match.im

@@ -0,0 +1,18 @@
+
+age = 65.
+yz = 32.
+
+p3 = 3.
+
+q = match yz in
+	1 => do
+            wq = 32.
+            wq * 2
+        end,
+
+	2       => age / 12,
+	p3      => age / 365,
+        5 | 6   => age = 32,
+        10..=15 => age = 64,
+	_       => 0
+end