Docsify broken in IE: Object doesn't support property or method 'startsWith'

[jhildenbiddle]

The String.prototype.startsWith() method is not available in legacy browsers like IE. This error completely breaks docsify sites in IE.

As a friendly reminder to the community, please keep docsify's supported browsers (IE10+) in mind when modifying docsify or plugins. Ideally, changes should be tested in target browsers (IE, Edge, Chrome, Firefox, and Safari) before going live. Free access to these browsers is available by signing up for a open source developer account with https://www.browserstack.com/, https://saucelabs.com/, or similar services.