Capability to fill other attr than href/src

Until now `customJs` and `customCSS` only create a `script` or `link` tags with `src` or `href`.

But there is no way to add/customize more attributes like `integrity`, `rel`, `type`, etc...

With new `customJS` and `customCSS` syntaxe is now possible, like following

```toml
[[params.customJS]]
  src = "https://cdnjs.cloudflare.com/ajax/libs/highlight.js/9.8.0/languages/go.min.js"
  integrity = "sha256-LVuWfOU0rWFMCJNl1xb3K2HSWfxtK4IPbqEerP1P83M="
  crossorigin = "anonymous"
  async = true
  defer = true
```

**ATTENTION** every keys of the map will be converted to tag attribute even if attribute is not part of _HTML_ spec.

Futhermore, in order to do not break existing configuration it still possible to use previous syntax:

```toml
customJS = ["https://cdnjs.cloudflare.com/ajax/libs/highlight.js/9.8.0/languages/go.min.js"]
```

**but you can't mix both syntax**, if you want to use new syntax you must first convert previous entries.

1 files changed, 5 insertions, 1 deletions

diff --git a/layouts/partials/head.html b/layouts/partials/head.html
index 5e27848..5447278 100644
--- a/layouts/partials/head.html
+++ b/layouts/partials/head.html
@@ -92,7 +92,11 @@
     <link rel="stylesheet" href="/css/style-h63bw1xth8vvjaqwlbjvebagy7w4erwpbhxigjixv5z0adzrhcquyjicocub.min.css" />
     <!--STYLES END-->
     {{ range .Site.Params.customCSS }}
-      <link rel="stylesheet" href="{{ . | absURL }}">
+      {{ if isset . "href" }}
+        <link{{ range $key, $value := . }} {{ if eq $key "href" }}{{ (printf "%s=\"%s\"" $key ($value | absURL)) | safeHTMLAttr }}{{ else }}{{ (printf "%s=\"%s\"" $key (string $value)) | safeHTMLAttr }}{{ end }}{{ end }}></script>
+      {{ else }}
+        <link rel="stylesheet" href="{{ . | absURL }}">
+      {{ end }}
     {{ end }}
 
     {{ if .Params.ga.async }}