Scripted qfn for SX1272

https://github.com/pointhi/kicad-footprint-generator/pull/250

https://www.semtech.com/uploads/documents/sx1272.pdf#page=125

QFN-28-1EP_6x6mm_P0.65mm_EP4.8x4.8mm:
  device_type: 'QFN'
  size_source: 'https://www.semtech.com/uploads/documents/sx1272.pdf#page=125'
  ipc_class: 'qfn' # 'qfn_pull_back'
  body_size_x:
    minimum: 5.9
    nominal: 6
    maximum: 6.1
  body_size_y:
    minimum: 5.9
    nominal: 6
    maximum: 6.1
  body_height:
    minimum: 0.8
    maximum: 1
  lead_width:
    minimum: 0.25
    nominal: 0.3
    maximum: 0.35
  lead_len:
    minimum: 0.3
    nominal: 0.4
    maximum: 0.5

  EP_size_x:
    minimum: 4.65
    nominal: 4.8
    maximum: 4.9
  EP_size_y:
    minimum: 4.65
    nominal: 4.8
    maximum: 4.9
  EP_num_paste_pads: [3, 3]


  thermal_vias:
    count: [4, 4]
    drill: 0.2
    paste_via_clearance: 0.1
    paste_between_vias: 1
    paste_rings_outside: 1
    grid: [0.95, 0.95]

  pitch: 0.65
  num_pins_x: 7
  num_pins_y: 7