Add regression test for rust-lang#13097

Author: GuillaumeGomez

tests/ui/doc/doc_markdown-issue_13097.fixed

@@ -0,0 +1,13 @@
+// This test checks that words starting with capital letters and ending with "ified" don't
+// trigger the lint.
+
+#![deny(clippy::doc_markdown)]
+
+pub enum OutputFormat {
+    /// `HumaNified`
+    //~^ ERROR: item in documentation is missing backticks
+    Plain,
+    // Should not warn!
+    /// JSONified console output
+    Json,
+}

tests/ui/doc/doc_markdown-issue_13097.rs

@@ -0,0 +1,13 @@
+// This test checks that words starting with capital letters and ending with "ified" don't
+// trigger the lint.
+
+#![deny(clippy::doc_markdown)]
+
+pub enum OutputFormat {
+    /// HumaNified
+    //~^ ERROR: item in documentation is missing backticks
+    Plain,
+    // Should not warn!
+    /// JSONified console output
+    Json,
+}

tests/ui/doc/doc_markdown-issue_13097.stderr

@@ -0,0 +1,18 @@
+error: item in documentation is missing backticks
+  --> tests/ui/doc/doc_markdown-issue_13097.rs:7:9
+   |
+LL |     /// HumaNified
+   |         ^^^^^^^^^^
+   |
+note: the lint level is defined here
+  --> tests/ui/doc/doc_markdown-issue_13097.rs:4:9
+   |
+LL | #![deny(clippy::doc_markdown)]
+   |         ^^^^^^^^^^^^^^^^^^^^
+help: try
+   |
+LL |     /// `HumaNified`
+   |         ~~~~~~~~~~~~
+
+error: aborting due to 1 previous error
+