Add M.2 connector footprint - socket

Hi,

adding a footprint for the M.2 socket. All the M.2 connectors I can find have the same footprint, except for the midplane type. The shape of the plastic differ across manufacturers, but only in details.

TE Connectivity: http://www.te.com/commerce/DocumentDelivery/DDEController?Action=showdoc&DocId=Customer+Drawing%7F2199230%7FB2%7Fpdf%7FEnglish%7FENG_CD_2199230_B2.pdf%7F1-2199230-6 Amphenol: https://www.amphenolcanada.com/ProductSearch/drawings/AC/MDTXXXXXX001.pdf JAE: https://www.jae.com/z-en/pdf_download_exec.cfm?param=SJ113503.pdf