docs(citation): add CITATION.cff file

Fixes #1226

CITATION.cff

@@ -0,0 +1,26 @@
+cff-version: 1.2.0
+message: "If you use this software, please cite it as below."
+authors:
+- family-names: "Lankes"
+  given-names: "Stefan"
+  orcid: "https://orcid.org/0000-0003-4718-2238"
+- family-names: "Finck"
+  given-names: "Colin"
+- family-names: "Kröning"
+  given-names: "Martin"
+  orcid: "https://orcid.org/0009-0005-0622-4229"
+- family-names: "Schulz"
+  given-names: "Frederik"
+- family-names: "Lambertz"
+  given-names: "Thomas"
+- family-names: "Klimt"
+  given-names: "Jonathan"
+  orcid: "https://orcid.org/0000-0002-5980-2214"
+- family-names: "Schwender"
+  given-names: "Jonathan"
+- family-names: "Krebs"
+  given-names: "Daniel"
+title: "Hermit Kernel"
+version: 0.8.0
+date-released: 2024-06-07
+url: "https://github.com/hermit-os/kernel"