Add 3 new Markdown emoji tests for newlines, emphasis, and links. The
goal of these tests is to ensure that Markdown operations concerning
emoji are preformed in proper order, with emoji being added correctly
based on other Markdown operations.
See suggestion here: https://git.io/flF5W.
This bug is caused by the conversion of newlines to `<br>` statements,
since `>` is not allowed as a character around an emoticon during
translation.
Also, add a new test case for preventing this bug from occurring in the
future.
Fix#9763.