Fix code that generates warning when submit to Mozilla.

[dteviot]

The Function constructor is eval. Warning: Evaluation of strings as code can lead to security vulnerabilities and performance issues, even in the most innocuous of circumstances. Please avoid using eval and the Function constructor when at all possible.

jszip/dist/jszip.min.js line 13 column 96498

Has been seen elsewhere. https://github.com/FooSoft/yomichan/issues/828#issuecomment-695272233 Not sure why it's showing now.