docs: Add link to PHP implementation by Conuti (#700)

Author: hf-kklein

README.rst

@@ -78,7 +78,7 @@ Andere nennenswerte BO4E Implementierungen
 * `Kotlin <https://github.com/openEnWi/ktBO4E-lib>`_
 * `TypeScript (handcrafted) <https://github.com/openEnWi/tsBO4E-lib>`_
 * `TypeScript (autogenerated, inherently consistent with the .NET library) <https://github.com/Hochfrequenz/bo4e-dotnet-ts-models>`_
-
+* `PHP <https://github.com/conuti-gmbh/bo4e-php/>` (und `Schemas <https://github.com/conuti-gmbh/bo4e-schema>`)
 
 .. _`BO4E website`: https://www.bo4e.de/dokumentation
 .. _`Contribution Guide`: CONTRIBUTING.md