Add support for MIME type application/x-directory

[smondet]

Nice: https://tzcomet.io//staging/#/token/KT1RJ6PbjHpwc3M5rw5s2Nbmefwbuwbdxton/12537

[damian0815]

hi @marklnichols @smondet - would you consider extending this to cover text/html as well? cf #85

[marklnichols]

Screenshots for text/html - not the best example as it contains a lot of white space to the sides of the image

[smondet]

https://tzcomet.io/staging/#/token/KT1Fxz4V3LaUcVFpvF8pAAx8G3Z4H7p7hhDg/1 https://tzcomet.io/staging/#/token/KT1WmAHNFxV1JzoGxQYEkE1aFKvNNNSj73sX/10000000003 https://tzcomet.io/staging/#/token/KT1RJ6PbjHpwc3M5rw5s2Nbmefwbuwbdxton/12537