1.2.1

• docs: update mention of imgix-core-js to @imgix/js-core (#87)
• docs: fixes routes and id (#86)
• fix: rename RequestError to APIError to match class name (#84)
• fix: specify APIError as a static class property (#82)
• feat: export APIError on ImgixAPI class (#80)
• refactor: remove optional chain operator for compatibility (#78)
• fix: remove ResponseError from request() return type (#78)
• fix: always stringify error data (#75)
• refactor: use standard function syntax for class method (#76)