DJI Osmo Pocket - Phone mount with case

Thanks to @twilliam and @DWONH for the gread desing!
I have some changes:
- optimes the size for osmo pocket holder, now you can put in and out really smooth
- moved the osmo holder a bit to front, now can use a silicone phone case / bumper
- modified the osmo holder for use with silicone phone case / bumper
- modified the bottom to print without support
- modified the bottom to stands alone.

For the phone holder parts you can use the original (slider and screw and nut)