v0.7.9: DataTable update - Change headerRender Prop

DataTable update - Allow React.FC in headerRender, disallow () => string:

Old: headerRender?: () => string | JSX.Element
New: headerRender?: React.FC | (() => JSX.Element)

Changed to allow use of state in the column header. Removed ability to return a string as it's not useful and complicates component. Use a template string in header prop if you want to use logic to render a string.