!! should format !!
test *emphasis* or _emphasis_ test

test **strong** or __strong__ test

Both **strong and _emphasis_ and *emphasis***.

Test ~~strikethrough~~ test

[expect]
test _emphasis_ or _emphasis_ test

test **strong** or **strong** test

Both **strong and _emphasis_ and _emphasis_**.

Test ~~strikethrough~~ test

!! should leave as-is when asterisk is in middle of word for GitHub ~~

*wor*d
*word*1
*word*?

[expect]
*wor*d
*word*1
_word_?