The following code in the preamble does the trick!
% hlink
\makeatletter
\newcommand*{\hlink}[2][]{%
\ifthenelse{\equal{#1}{}}%
{\href{#2}{#2}}%
{\href{#2}{#1}}}
\makeatother
% social
\makeatletter
\newcommand*{\facebooksocialsymbol}{\faFacebook~}
\newcommand\faSkype{{\FA\symbol{"F17E}}}
\newcommand*{\skypesocialsymbol}{\faSkype~}
\RenewDocumentCommand{\social}{O{}O{}m}{%
\ifthenelse{\equal{#2}{}}%
{%
\ifthenelse{\equal{#1}{linkedin}}{\collectionadd[linkedin]{socials}{\protect\httplink[#3]{www.linkedin.com/in/#3}}}{}%
\ifthenelse{\equal{#1}{twitter}} {\collectionadd[twitter]{socials} {\protect\httplink[#3]{www.twitter.com/#3}}} {}%
\ifthenelse{\equal{#1}{facebook}}{\collectionadd[facebook]{socials}{\protect\httplink[#3]{www.facebook.com/#3}}} {}%
\ifthenelse{\equal{#1}{github}} {\collectionadd[github]{socials} {\protect\httplink[#3]{www.github.com/#3}}} {}%
\ifthenelse{\equal{#1}{skype}} {\collectionadd[skype]{socials} {\protect\hlink[#3]{skype:#3}}} {}%
}
{\collectionadd[#1]{socials}{\protect\httplink[#3]{#2}}}}
\makeatother
Step by step explanation:
Create a "hlink" command: This is needed because the skype link is not a link to a web page
\makeatletter
\newcommand*{\hlink}[2][]{%
\ifthenelse{\equal{#1}{}}%
{\href{#2}{#2}}%
{\href{#2}{#1}}}
\makeatother
Create commands for the symbols that will be used. Note that the skype symbol is not in the default Font Awesome command sets and thus needs a different solution than the facebook symbol
\newcommand*{\facebooksocialsymbol}{\faFacebook~}
\newcommand\faSkype{{\FA\symbol{"F17E}}}
\newcommand*{\skypesocialsymbol}{\faSkype~}
Lastly, edit the original social command to include these symbols:
\RenewDocumentCommand{\social}{O{}O{}m}{%
\ifthenelse{\equal{#2}{}}%
{%
\ifthenelse{\equal{#1}{linkedin}}{\collectionadd[linkedin]{socials}{\protect\httplink[#3]{www.linkedin.com/in/#3}}}{}%
\ifthenelse{\equal{#1}{twitter}} {\collectionadd[twitter]{socials} {\protect\httplink[#3]{www.twitter.com/#3}}} {}%
\ifthenelse{\equal{#1}{facebook}}{\collectionadd[facebook]{socials}{\protect\httplink[#3]{www.facebook.com/#3}}} {}%
\ifthenelse{\equal{#1}{github}} {\collectionadd[github]{socials} {\protect\httplink[#3]{www.github.com/#3}}} {}%
\ifthenelse{\equal{#1}{skype}} {\collectionadd[skype]{socials} {\protect\hlink[#3]{skype:#3}}} {}%
}
{\collectionadd[#1]{socials}{\protect\httplink[#3]{#2}}}}
\makeatother