Add README.

Author: ilopX

patterns/interpreter/conceptual/README.md

@@ -0,0 +1,42 @@
+# Interpreter Pattern
+In computer programming, the interpreter pattern is a design pattern that specifies how to evaluate 
+sentences in a language. 
+
+## Diagram:
+![Interpreter Diagram](https://user-images.githubusercontent.com/8049534/176169636-4c8eb3ba-d5e8-4ecb-81a8-96f1a30f6339.png)
+
+## Client code:
+```dart
+void main() {
+  final context = Context();
+  final variable1 = BoolVariable('var1');
+  final variable2 = BoolVariable('var2');
+  final variable3 = BoolVariable('var3');
+  final variable4 = BoolVariable('var4');
+
+  context.assign(variable1, true);
+  context.assign(variable2, false);
+  context.assign(variable3, true);
+  context.assign(variable4, false);
+
+  final expression = And(
+    variable1, // true
+    Xor(
+      variable2, // false
+      Or(
+        variable3, // true
+        variable4, // false
+      ),
+    ),
+  );
+
+  print(expression.evaluate(context));
+  print(expression.toDebugString(context));
+}
+```
+
+### Output:
+```
+var4(false) Or var3(true) Xor var2(false) And var1(true)
+result: true
+```