ci(appveyor): Install phantomjs on AppVeyor

.appveyor.yml

@@ -2,7 +2,7 @@
 install:
   - sc config wuauserv start= auto
   - net start wuauserv
-  - cinst php composer ffmpeg
+  - cinst php composer ffmpeg phantomjs
   - refreshenv
   - copy C:\tools\php72\php.ini-development C:\tools\php72\php.ini
   - echo extension=C:\tools\php72\ext\php_gmp.dll >> C:\tools\php72\php.ini

config/config_test_windows.yml

@@ -3,6 +3,7 @@ convert: false
 python: C:\Python36\python.exe
 avconv: C:\ProgramData\chocolatey\bin\ffmpeg.exe
 avconvVerbosity: fatal
+phantomjsDir: C:\ProgramData\chocolatey\bin\
 youtubedl: C:\Python36\Lib\site-packages\youtube_dl\__main__.py
 params:
     - --no-warnings