Fix broken PDF build

[Holzhaus]

The PDF build currently fails:

[...]

! Package inputenc Error: Unicode character ✘ (U+2718)
(inputenc)                not set up for use with LaTeX.

See the inputenc package documentation for explanation.
Type  H <return>  for immediate help.
 ...

l.21919 ✘

(That makes 100 errors; please try again.)
!  ==> Fatal error occurred, no output PDF file produced!
Transcript written on Mixxx-Manual.log.
=== TeX engine is 'pdfTeX'
Latexmk: Index file 'Mixxx-Manual.idx' was written
Latexmk: Missing input file: 'None' from line
  '! LaTeX Error: File `None' not found.'
Latexmk: Missing input file: 'None' from line
  '! LaTeX Error: File `None' not found.'
Latexmk: Missing input file: 'None' from line
  '! LaTeX Error: File `None' not found.'
Latexmk: Missing input file: 'None' from line
  '! LaTeX Error: File `None' not found.'
Failure to make 'Mixxx-Manual.pdf'
Latexmk: Summary of warnings from last run of (pdf)latex:
  =====Latex reported missing or unavailable character(s).
=====See log file for details.
Latexmk: Errors, in force_mode: so I tried finishing targets
Collected error summary (may duplicate other messages):
  pdflatex: Command for 'pdflatex' gave return code 1
      Refer to 'Mixxx-Manual.log' for details
make[1]: *** [Makefile:29: Mixxx-Manual.pdf] Error 12
make[1]: Leaving directory '/home/jan/Projects/mixxx-manual/build/latex'
make: *** [Makefile:121: latexpdf] Error 2

[Holzhaus]

Apparently SVG files in Latex PDFs is unsupported as well. I'll check for a workaround.

[Holzhaus]

Apparently SVG files in Latex PDFs is unsupported as well. I'll check for a workaround.

This can be fixed by using sphinx.ext.imgconverter, see sphinx-doc/sphinx#1907.