add command `seed` to db manager to seed db with examples
add command `seed` to db manager to seed db with examples

ChristopherChudzicki/math3d,stardust66/math3d,stardust66/math3d,ChristopherChudzicki/math3d,ChristopherChudzicki/math3d,stardust66/math3d,stardust66/math3d,ChristopherChudzicki/math3d