feat(docs): add stable links for external sites (#9620)

* add stable links for external docs
this is usefull for the CII best practices badge and other sites where we might need stable links; assuming we maintain control of docs.inventree.org seems like a stable bet with current structures

* fix checking logic

* fix link target

docs/requirements.txt

@@ -306,6 +306,7 @@ mkdocs==1.6.1 \
     #   mkdocs-include-markdown-plugin
     #   mkdocs-macros-plugin
     #   mkdocs-material
+    #   mkdocs-redirects
     #   mkdocs-simple-hooks
     #   mkdocstrings
     #   neoteroi-mkdocs
@@ -339,6 +340,10 @@ mkdocs-material-extensions==1.3.1 \
     --hash=sha256:10c9511cea88f568257f960358a467d12b970e1f7b2c0e5fb2bb48cab1928443 \
     --hash=sha256:adff8b62700b25cb77b53358dad940f3ef973dd6db797907c49e3c2ef3ab4e31
     # via mkdocs-material
+mkdocs-redirects==1.2.2 \
+    --hash=sha256:3094981b42ffab29313c2c1b8ac3969861109f58b2dd58c45fc81cd44bfa0095 \
+    --hash=sha256:7dbfa5647b79a3589da4401403d69494bd1f4ad03b9c15136720367e1f340ed5
+    # via -r docs/requirements.in
 mkdocs-simple-hooks==0.1.5 \
     --hash=sha256:dddbdf151a18723c9302a133e5cf79538be8eb9d274e8e07d2ac3ac34890837c \
     --hash=sha256:efeabdbb98b0850a909adee285f3404535117159d5cb3a34f541d6eaa644d50a