Suggest not exist/nonexistent

Author: jsoref

.github/actions/spelling/line_forbidden.patterns

@@ -602,6 +602,9 @@ CLoud
 # Should be `did not exist`
 \bwere not existent\b
 
+# Should be `not exist` or `nonexistent`
+(?<!(?i)IF|WHERE )\bnot exists\b
+
 # Should be `nonexistent`
 \bnon existing\b