Add regression test for #10262

Author: GuillaumeGomez

tests/ui/doc/issue_10262.fixed

@@ -0,0 +1,8 @@
+#![warn(clippy::doc_markdown)]
+
+// Should only warn for the first line!
+/// `AviSynth` documentation:
+//~^ ERROR: item in documentation is missing backticks
+///
+/// > AvisynthPluginInit3 may be called more than once with different IScriptEnvironments.
+pub struct Foo;

tests/ui/doc/issue_10262.rs

@@ -0,0 +1,8 @@
+#![warn(clippy::doc_markdown)]
+
+// Should only warn for the first line!
+/// AviSynth documentation:
+//~^ ERROR: item in documentation is missing backticks
+///
+/// > AvisynthPluginInit3 may be called more than once with different IScriptEnvironments.
+pub struct Foo;

tests/ui/doc/issue_10262.stderr

@@ -0,0 +1,15 @@
+error: item in documentation is missing backticks
+  --> tests/ui/doc/issue_10262.rs:4:5
+   |
+LL | /// AviSynth documentation:
+   |     ^^^^^^^^
+   |
+   = note: `-D clippy::doc-markdown` implied by `-D warnings`
+   = help: to override `-D warnings` add `#[allow(clippy::doc_markdown)]`
+help: try
+   |
+LL | /// `AviSynth` documentation:
+   |     ~~~~~~~~~~
+
+error: aborting due to 1 previous error
+