Add Danish README & CONTRIBUTION (#812)

* Added Danish translation

* Cleaned up a spelling mistake

* Corrected spelling mistake

* Added Danish references

* chore: Rebase README.da.md

Co-authored-by: Andrew Rump <ar@businessnow.dk>
Co-authored-by: James Harris <wopian@wopian.me>

CONTRIBUTING.md

@@ -2,6 +2,7 @@
 
 🎌
 [Čeština][CZ],
+[Dansk][DA],
 [Deutsch][DE],
 **English**,
 [Español][ES],
@@ -23,6 +24,7 @@
 
 [AR]:CONTRIBUTING.ar.md
 [CZ]:CONTRIBUTING.cz.md
+[DA]:CONTRIBUTING.da.md
 [DE]:CONTRIBUTING.de.md
 [EN]:CONTRIBUTING.md
 [ES]:CONTRIBUTING.es.md