refs #19529 [fid_bbi] fix translations and misspelled resources in Amsl

* change wording of "Create Account"
* accessibility page: add full stop and new paragraph
* fix translations in search
** result page, facets
** advanced search form: tranlation of slimselect placeholder and empty results
* fix some search links
* refactoring of "misspelled resources" mapping
** now uses YAML
** enables use of special characters
* add some source mappings
* adapted BASE to new page structure
* 18826 accessibility information page, including footer link
* 18995 AMSL Sources page explanatory line in German
TODO add english translation
* 18995 fix some AMSL Source scope notes
* 19399 start page, "about us", and "for subject librarians"