Broken strikethrough of plain email text: ~~e@m.co~~

[cayuu]

Describe the bug
When GFM is true, the following text:

~~hello@email.com~~

Renders as:

<a href="mailto:~~hello@email.com">~~hello@email.com</a>~~

In HTML it thus shows up as something like (but not exactly, the mailto should render as above - see the Markdown demo for exact behaviour, Github's parser is harder to coerce to the invalid rendering):

~~hello@email.com~~

To Reproduce
Steps to reproduce the behavior:

Simply type ~~hello@email.com~~ into the Demo.

Expected behavior
Expect the following output

<del><a href="mailto:hello@email.com">hello@email.com</a></del>