Merge branch 'provider-slugs' into 'master'

Provider slugs

See merge request !19

wikidata.yml

@@ -658,7 +658,7 @@
   url_pattern: 'http://www.hls-dhs-dss.ch/textes/d/D$1.php'
   identifier_rule: >-
     [0-9]+
-- slug: Ortsnamen
+- slug: ortsnamen
   alias: []
   name:
     de: Ortsnamen
@@ -672,7 +672,7 @@
   url_pattern: 'https://search.ortsnamen.ch/record/$1'
   identifier_rule: >-
     [0-9]+
-- slug: Fundmuenzen
+- slug: fundmuenzen
   alias: []
   name:
     de: Fundmuenzen