Add .deb specific dependencies

[veggiedefender]

Contributor checklist

• My contribution is fully baked and ready to be merged as is
• My changes are rebased on the latest master branch
• My commits are in nice logical chunks
• I have followed the best practices in my commit messages
• I have tested my contribution on these platforms:

• Debian docker image on Arch 4.14.3-1-ARCH

• My changes pass all the local tests 100%
• I have considered whether my changes need additional tests, and in the case they do, I have written them

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Description

Adds libasound2 and libxss1 to the generated .deb's dependencies, as well as the default .deb dependencies included by electron-builder (["gconf2", "gconf-service", "libnotify4", "libappindicator1", "libxtst6", "libnss3"]).

Probably fixes #1838, but @angelo-v should probably test this out first, since I can't get my docker setup to open windows on my host OS.

[angelo-v]

Sorry, cannot test this atm, but here is my Dockerfile:

FROM ubuntu:latest        

RUN apt-get update -y && apt-get install curl apt-transport-https -y                                     
RUN curl -s https://updates.signal.org/desktop/apt/keys.asc | apt-key add -                              
RUN echo "deb [arch=amd64] https://updates.signal.org/desktop/apt xenial main" | tee -a /etc/apt/sources.list.d/signal-xenial.list 
RUN apt-get update -y && apt-get install signal-desktop -y                                               

CMD signal-desktop 

And the run command:

docker run -ti --rm \                                                                                                                                                                                
       -e DISPLAY=$DISPLAY \
       -v /tmp/.X11-unix:/tmp/.X11-unix \
       signal

[veggiedefender]

Working great!