docs: fix spellcheck errors

Signed-off-by: Francesco Canovai <francesco.canovai@enterprisedb.com>

Author: fcanovai

.wordlist.txt

@@ -36,6 +36,7 @@ cnpg
 codebase
 csi
 customresourcedefinition
+devel
 externalClusters
 gcs
 gf
@@ -47,6 +48,7 @@ io
 isWALArchiver
 kubectl
 kubernetes
+md
 minio
 namespace
 namespaces
@@ -65,6 +67,7 @@ sc
 selfsigned
 serverName
 serviceaccount
+sig
 storageClass
 tfddg
 tgz