Added Mastodon social link

[csarnataro]

Added a configuration for Mastodon social, updated the list of social link. Updated README accordingly.

[arifszn]

Haven't heard of mastodon before but sounds promising as a new social network.

Seems the user would need to add the verification link manually. Sounds a bit complex in terms of the general user. That's why not planning to add this currently. The goal of this project is to make a portfolio builder as easy as possible. That's why we try to keep features simple.

[arifszn]

I intend to sign up for Mastodon and might reopen this PR.

[csarnataro]

I see, and it makes sense.
Regarding the verification link, it's an optional feature, a user doesn't need to implement it to have an account on Mastodon.
Just to let you know, I have implemented the Mastodon link in my fork at csarnataro.github.io

Again, thank you for this project.

[arifszn]

Let's add this. But remove the verification link. An advance user should be able to figure that out by himself.

[csarnataro]

Hi @arifszn
I've removed the verification link instructions from the README file.