className attribute is always overwritten regardless of what lineProps returns

[Zo0x]

Describe the bug
lineProps is currently unable to set the className because its always overwritten, regardless of what lineProps does.

var properties = typeof lineProps === 'function' ? lineProps(lineNumber) : lineProps;
properties['className'] = className;

https://github.com/react-syntax-highlighter/react-syntax-highlighter/blob/master/src/highlight.js#L108

A super-simple fix would be to simply change those two lines to this:

var properties = {className: className, ...typeof lineProps === 'function' ? lineProps(lineNumber) : lineProps};

This affects both Prism and Highlight.js, as well as countless third-party dependencies that use this behaviour to change props on a per-line basis.

This is currently making this package, as well as those that rely on it, completely unusable for me, is there any sort of roadmap as to when this issue is going to be resolved?

To Reproduce
Steps to reproduce the behavior:

1. set className using lineProps
2. value is always overwritten

Expected behavior
Class names set in lineProps shouldn't be blindly overwritten.

[shughes-uk]

React will complain at you but a workaround is possible by passing

lineProps={{class:"class-name"}