[dockerfile] add fontconfig, to see if this is what causes errors on CI

E.g.:
https://gitlab.iscpif.fr/gargantext/haskell-gargantext/-/jobs/18643

paginating QuantumComputing corpus works (MapTerms):            Fontconfig error: Cannot load default config file: No such file: (null)
Fontconfig error: No writable cache directories

bin/gargantext-cli/CLI/Ini.hs

@@ -61,7 +61,11 @@ iniParser = fmap CCMD_ini $ IniArgs <$>
   (optional . strOption $ long "toml-path" <> help "Path to the output .toml file") <*>
   (flag False True (long "dry-run" <> help "If set, will only output generated .toml file to stdout"))
 
-convertConfigs :: Ini.GargConfig -> IniMail.MailConfig -> IniNLP.NLPConfig -> PGS.ConnectInfo -> Config.GargConfig
+convertConfigs :: Ini.GargConfig
+               -> IniMail.MailConfig
+               -> IniNLP.NLPConfig
+               -> PGS.ConnectInfo
+               -> Config.GargConfig
 convertConfigs ini@(Ini.GargConfig { .. }) iniMail nlpConfig connInfo =
   Config.GargConfig { _gc_secrets = CTypes.SecretsConfig { _s_master_user = _gc_masteruser
                                                          , _s_secret_key = _gc_secretkey

devops/docker/Dockerfile

@@ -17,6 +17,7 @@ RUN apt-get update && \
       apt-transport-https \
       ca-certificates \
       curl \
+      fontconfig \
       git \
       gnupg2 \
       locales \