Allow .msg extension as a receipt type

Many of our vendors will email me when our cards are charged and the payment has gone through. Those emails get automatically forwarded to Expensify, but because .msg isn't an approved extension type, Expensify isn't recognizing these emails as receipts and not attaching them to payments.

Another improvement could be to simply allow .msg as an allowed extension type so that I can drag and drop items from the inbox into the receipt section. This still takes a fair bit of labor, but much less so than having to convert each email into a pdf.

See attached example.