RFC: Always add a space after the `function` keyword (#3903)
* Always add a space after the `function` keyword
* WIP update snapshots
* WIP put generator function asterisk before space
https://github.com/prettier/prettier/issues/3847#issuecomment-363449250
* WIP update snapshots
* Add changelog
* Add tests for anonymouse generator function
* print space between `function` and generator star
* update changelog
* print space between yield and *
Co-authored-by: Joseph Frazier <1212jtraceur@gmail.com>
Co-authored-by: Sosuke Suzuki <aosukeke@gmail.com>
Co-authored-by: Georgii Dolzhykov <thorn.mailbox@gmail.com>
