message: [jest-editor-support] update definition
  According to (the implementation)[https://github.com/facebook/jest/blob/f4f51914d577dc53748f599f3f626dfe3154883e/packages/jest-editor-support/src/Snapshot.js#L106] the first parameter of Snapshot constructor is optional.
diff: @@ -179,6 +179,6 @@ export interface SnapshotMetadata {
  }
  export class Snapshot {
  - constructor(parser: any, customMatchers?: string[]);
  + constructor(parser?: any, customMatchers?: string[]);
  getMetadata(filepath: string): SnapshotMetadata[];
  }
  