Try and allow the user to disable external css

resources/index.html

@@ -5,13 +5,13 @@
         <meta name="viewport" content="width=device-width, initial-scale=1.0" />
         <link
             rel="stylesheet"
-            href="https://cdnjs.cloudflare.com/ajax/libs/spectre.css/0.5.8/spectre.min.css"
+            href="{{ themepath }}spectre.min.css"
             integrity="sha256-J24PZiunX9uL1Sdmbe6YT9kNuV5lfVxj3A6Kij5UP6k="
             crossorigin="anonymous"
         />
         <link
             rel="stylesheet"
-            href="https://cdnjs.cloudflare.com/ajax/libs/spectre.css/0.5.8/spectre-icons.min.css"
+            href="{{ themepath }}spectre-icons.min.css"
             integrity="sha256-LxdDS9G94ArUz2UYVPo5FhSeD4owwcBFAQv2Nl1dNUU="
             crossorigin="anonymous"
         />

src/setup.rs

@@ -88,6 +88,8 @@ pub struct Config {
 #[derive(Serialize, Deserialize, Clone)]
 #[cfg_attr(not(feature = "dev"), serde(default))]
 pub struct HighlightConfig {
+    /// Path to the theme to use
+    pub themepath: String,
     /// Theme to use
     pub theme: String,
     /// Additional languages to include
@@ -120,6 +122,7 @@ impl Default for Config {
 impl Default for HighlightConfig {
     fn default() -> Self {
         Self {
+            themepath: "https://cdnjs.cloudflare.com/ajax/libs/spectre.css/0.5.8/".to_owned(),
             theme: "github".to_owned(),
             languages: vec!["rust".to_owned()],
         }