test: 添加 Demo22 演示项目

playground/Demo/Demo22/Main.snow

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+module: Main
+    import: os,ModuleA
+    globals:
+        declare sum: int = 3
+    function: main
+        returns: void
+        body:
+            sum = sum + ModuleA._sum(1, 2)
+            os.print(sum)
+        end body
+    end function
+end module

playground/Demo/Demo22/ModuleA.snow

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+module: ModuleA
+    function: _sum
+        params:
+            declare a: int
+            declare b: int
+        returns: int
+        body:
+            return a + b
+        end body
+    end function
+end module

playground/Demo/Demo22/OS.snow

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+module: os
+    import: os
+    function: print
+        params:
+            declare i1: int
+        returns: void
+        body:
+            syscall("PRINT",i1)
+        end body
+    end function
+end module