Add param for custom CSS

Fix #36

README.md

@@ -70,6 +70,12 @@ disqusShortname = "xxxxxx"
 
 This option enables the KaTeX auto-render extension. To render block math, use `$$ ... $$`. For inline math, use `\\( ... \\)`. For more details, please refer to https://github.com/KaTeX/KaTeX/blob/v0.7.1/contrib/auto-render/auto-render.js#L73 .
 
+### Custom CSS
+```
+[params]
+    customCss = ["css/foo.css"]
+```
+
 ### Others
 
 For other configuration variables, visit [Hugo documentation](https://gohugo.io/overview/configuration/#configuration-variables).

layouts/partials/head.html

@@ -15,6 +15,9 @@
     <link href="{{ "webfonts/source-code-pro/main.css" | absURL }}" rel="stylesheet" type="text/css">
 
     <link rel="stylesheet" href="{{ "css/style.css" | absURL }}">
+    {{ range .Site.Params.customCss -}}
+        <link rel="stylesheet" href="{{ . | absURL }}">
+    {{- end }}
 
     {{ hugo.Generator }}
 </head>