Add `pipe` or `stdin` as a valid Source URL for `./wstools export`

[ronelm2000]

Allows wsmtools to accept input from pipe/stdin. Currently, the only parser the should require this input should be Deck JSON Deck Parser.

Sample Usage:

# This command will get Deck Data from EncoreDecks, replace base rarity cards with my foil cards, then export to TTS.
./wstools merge https://www.encoredecks.com/deck/UFo2ADuKC ./path/to/my_foil_cards.json | ./wstools export pipe --with upscaling,sendtcp --exporter tts --out sharex