Add Skymu to list of the clients

[nilFinx]

The client isn't that complete, but it has basic IM and conferences now, so I think that it is good enough to be added here.

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This change is 

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Build failed. Please check the logs.

[nilFinx]

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 > [11/17] RUN ["make", "toktok/spec.md"]:
0.403     | sed -e '/``` haskell/,/```/d'	\
0.403   >> ../toktok/spec.md;				\
0.403   find . -name "*.lhs" -delete;		\
0.403   git checkout .;			\
0.403 }
0.404 /usr/bin/pandoc
0.486 pandoc: src/Network/Tox.tex: withBinaryFile: does not exist (No such file or directory)
0.503 Updated 57 paths from the index
0.507 grep Introduction toktok/spec.md
0.508 make: *** [Makefile:27: toktok/spec.md] Error 1
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Dockerfile:30
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  28 |     
  29 |     COPY --chown=builder:builder toktok/spec.md.dist /home/builder/build/toktok/
  30 | >>> RUN ["make", "toktok/spec.md"]
  31 |     
  32 |     COPY --chown=builder:builder toktok/ /home/builder/build/toktok/
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ERROR: failed to build: failed to solve: process "make toktok/spec.md" did not complete successfully: exit code: 2

Not me.