refactor: create src dir

maxun-core/src/index.ts

@@ -0,0 +1,8 @@
+import Interpreter from './interpret';
+
+export default Interpreter;
+export { default as Preprocessor } from './preprocessor';
+export type {
+  WorkflowFile, WhereWhatPair, Where, What,
+} from './types/workflow';
+export { unaryOperators, naryOperators, meta as metaOperators } from './types/logic';