add source maps to npm package

[melnikaite]

My dev tool in chrome complains about source maps Files are really missing in folder node_modules/minio/dist/main/

DevTools failed to parse SourceMap: file:///Users/me/projects/backend/node_modules/minio/dist/main/minio.js.map
DevTools failed to parse SourceMap: file:///Users/me/projects/backend/node_modules/minio/dist/main/helpers.js.map
DevTools failed to parse SourceMap: file:///Users/me/projects/backend/node_modules/minio/dist/main/signing.js.map
DevTools failed to parse SourceMap: file:///Users/me/projects/backend/node_modules/minio/dist/main/errors.js.map
DevTools failed to parse SourceMap: file:///Users/me/projects/backend/node_modules/minio/dist/main/object-uploader.js.map
DevTools failed to parse SourceMap: file:///Users/me/projects/backend/node_modules/minio/dist/main/transformers.js.map
DevTools failed to parse SourceMap: file:///Users/me/projects/backend/node_modules/minio/dist/main/xml-parsers.js.map
DevTools failed to parse SourceMap: file:///Users/me/projects/backend/node_modules/minio/dist/main/s3-endpoints.js.map
DevTools failed to parse SourceMap: file:///Users/me/projects/backend/node_modules/minio/dist/main/notification.js.map

[kannappanr]

@melnikaite We will take a look at the issue and get back to you