message: Fix Extract Interface on exported class declarations
  Closes
diff: @@ -187,6 +187,28 @@ class AnotherPosition implements Extracted {
  interface Extracted {
  isEqualTo(position: Position): boolean;
  +}`
  + },
  + {
  + description: "an exported class",
  + code: `export class Foo[cursor] {
  + constructor(readonly numbers: number[]) {}
  +
  + bar(): number {
  + return this.numbers.length;
  + }
  +}`,
  + expected: `export class Foo implements Extracted {
  + constructor(readonly numbers: number[]) {}
  +
  + bar(): number {
  + return this.numbers.length;
  + }
  +}
  +
  +interface Extracted {
  + readonly numbers: number[];
  + bar(): number;
  }`
  }
  ],
  