Fix a typo and add mailto: to the email link

[PetitPotiron]

Hello,
Thank you for such a beautiful theme!

In this PR, I made 2 edits:

1. I corrected typos (galley -> gallery) in the README (a2d73b1).
2. I added mailto: to the email address social link in the footer (6b4e2f0) .

I am not completely sure if the second (6b4e2f0) commit is a good idea though. The current problem is, clicking on the link does not lead to any email creation for the _config.yml site.rrss.email being configured to email@example.com (see Mailto on Wikipedia).

However, changing such a value would not be backward-compatible as some users (may) have already changed the value of site.rrss.email to mailto:email@example.com.

Although, as wind is a small theme with not that many users (I assume?), it would not be a major problem. In addition, not a lot of people set this value.

To illustrate, among the 19 forks of this repository, only two did set the email value:

• one did change its value to mailto:email@example.com (see here)
• the other one sticked to the suggested email@example.com value (see here)

If we decide to revert the second (6b4e2f0) commit, we definitely have to change the README or at least the _config.yml comments to explain that the blogger has to set-up their email address to mailto:email@example.com. It is not obvious otherwise.

[a-chacon]

@PetitPotiron thank you! I think there are no problems with the forks, they can update it later if needed. Thanks again.