Add Vale check for missing punctuation between sentences

.vale/styles/FernStyles/SentencePunctuation.yml

@@ -0,0 +1,14 @@
+extends: existence
+message: "Missing punctuation between sentences. Add ., ?, !, or ;"
+link: https://learn.microsoft.com/en-us/style-guide/punctuation/periods
+level: warning
+scope: paragraph
+nonword: true
+
+# Heuristics:
+# 1) Previous token ends with a lowercase letter/digit/closer, then a space, then a common sentence-starter (trimmed to reduce false positives).
+# 2) Previous token ends with a lowercase letter/digit/closer, then a space, then a Capitalized word followed by a common auxiliary/verb.
+# These aim to reduce false positives like "API Reference" and "John Smith".
+tokens:
+  - '([a-z0-9\)\]])[ \t]+(This|That|These|Those|We|You|They|It|I|However|Therefore|Then|Next|Finally|Also|Note|If|When|While|After|Before)\b'
+  - '([a-z0-9\)\]])[ \t]+([A-Z][a-z]+)[ \t]+(is|are|was|were|has|have|can|could|should|will|would|do|does|did)\b'