Add some edge cases to the documentation of Path

Affected methods are `starts_with` and `strip_prefix`.

Author: tbu-

src/libstd/path.rs

@@ -1869,7 +1869,11 @@ impl Path {
     ///
     /// let path = Path::new("/test/haha/foo.txt");
     ///
+    /// assert_eq!(path.strip_prefix("/"), Ok(Path::new("test/haha/foo.txt")));
     /// assert_eq!(path.strip_prefix("/test"), Ok(Path::new("haha/foo.txt")));
+    /// assert_eq!(path.strip_prefix("/test/"), Ok(Path::new("haha/foo.txt")));
+    /// assert_eq!(path.strip_prefix("/test/haha/foo.txt"), Ok(Path::new("")));
+    /// assert_eq!(path.strip_prefix("/test/haha/foo.txt/"), Ok(Path::new("")));
     /// assert_eq!(path.strip_prefix("test").is_ok(), false);
     /// assert_eq!(path.strip_prefix("/haha").is_ok(), false);
     /// ```
@@ -1900,6 +1904,9 @@ impl Path {
     /// let path = Path::new("/etc/passwd");
     ///
     /// assert!(path.starts_with("/etc"));
+    /// assert!(path.starts_with("/etc/"));
+    /// assert!(path.starts_with("/etc/passwd"));
+    /// assert!(path.starts_with("/etc/passwd/"));
     ///
     /// assert!(!path.starts_with("/e"));
     /// ```