Accept an Option<&str> as a link name

Many users may be adding links to their documents with &'static str's as the name, which means that they would manually have to convert to an Option<String>, leading to code that looks like `link("gemini://emii.gay", Some(String::from("My Website")))` instead of the simpler `link("gemini://emii.gay/", Some("My Website"))`.

We can change this method to accept the latter in addition to accepting `Option<String>`s, which might make users lives a little easier

gemtext/src/lib.rs

@@ -18,10 +18,14 @@ impl Builder {
         self
     }
 
-    pub fn link<T: Into<String>>(mut self, to: T, name: Option<String>) -> Builder {
+    pub fn link<T, S>(mut self, to: T, name: Option<S>) -> Self
+    where
+        T: Into<String>,
+        S: Into<String>,
+    {
         self.nodes.push(Node::Link {
             to: to.into(),
-            name: name,
+            name: name.map(Into::into),
         });
         self
     }