R1:26b29a60c0f8

Remarkup rule to embed images

Summary:
Ref T4190. Added the remarkup rule to embed images:

Syntax is as follows:

`{image <IMAGE_URL>}`

Parameters are also supported, like:
`{image uri=<IMAGE_URI>, width=500px, height=200px, alt=picture of a moose, href=google.com}`

URLs without a protocol are not supported.

Test Plan: Tested with many of the syntax variations. If the provided URL doesn't point to an image, then a broken image icon will be shown.

Reviewers: epriestley, #blessed_reviewers

Reviewed By…