IE 11 compatibility issue due to startsWith

[cvetanov]

Describe the bug
Application does not work in IE due to not supported method startsWith.

To reproduce
Any React application trying to use the launchdarkly-react-client-sdk package.

Expected behavior
Should work in IE since the docs do not mention adding a polyfill for String.prototype.startsWith and seems like it was fixed in a previous version of the client SDK

Current workaround
Adding a polyfill for String.prototype.startsWith ourselves.

Logs
Object doesn't support property or method 'startsWith'

SDK version
"launchdarkly-react-client-sdk": "^2.12.4"

Language version, developer tools
Not sure if relevant, but we are on React v16.8.6

OS/platform
Browser IE 11

Additional context
Most probably caused by the condition in here.

[eli-darkly]

Thanks for catching this! We'll have a patch out shortly.

[eli-darkly]

Fixed in the 2.12.5 release.