Add benchmark project

Signed-off-by: moznion <moznion@mail.moznion.net>

Author: moznion

examples/benchmark/.gitignore

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+using_transformer.js
+

examples/benchmark/README.md

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+# benchmark
+
+This project does benchmark of object marshalling into DynamoDB atributes between ts-dynamodb-attributes-transformer and [kayomarz/dynamodb-data-types](https://github.com/kayomarz/dynamodb-data-types).
+
+## How to run
+
+```
+npm ci
+npm run bench
+```
+
+## Example result
+
+```
+node version: v16.17.0
+dynamodb-data-types marshalling x 3,475,450 ops/sec ±0.45% (96 runs sampled)
+ts-dynamodb-attributes-transformer marshalling x 13,405,409 ops/sec ±0.43% (91 runs sampled)
+Fastest is ts-dynamodb-attributes-transformer marshalling
+```
+

examples/benchmark/dynamodb_data_types.js

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+const AttributeValue = require('dynamodb-data-types').AttributeValue;
+
+const obj = {
+  id: 12345,
+  name: 'John Doe',
+  tags: {
+    foo: 'bar',
+    buz: 'qux',
+  },
+  flags: ['foo', 'bar'],
+  nil: null,
+};
+
+function toDynamoDBRecord() {
+  AttributeValue.wrap(obj);
+}
+
+module.exports = toDynamoDBRecord;

examples/benchmark/index.js

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+const Benchmark = require('benchmark');
+const toDynamoDBRecordByDataTypes = require('./dynamodb_data_types');
+const toDynamoDBRecordByTransformer = require('./using_transformer').toDynamoDBRecord;
+
+console.log(`node version: ${process.version}`);
+new Benchmark.Suite()
+  .add('dynamodb-data-types marshalling', function () {
+    toDynamoDBRecordByDataTypes();
+  })
+  .add('ts-dynamodb-attributes-transformer marshalling', function () {
+    toDynamoDBRecordByTransformer();
+  })
+  .on('cycle', function (event) {
+    console.log(String(event.target));
+  })
+  .on('complete', function () {
+    console.log('Fastest is ' + this.filter('fastest').map('name'));
+  })
+  .run({ async: true });