Point out that docs are open source and can be edited (#1033)

* Point out that docs are open source and can be edited
Signed-off-by: Julius Volz <julius.volz@gmail.com>

* Add contribution clarifications to README.md, link to it
Signed-off-by: Julius Volz <julius.volz@gmail.com>

README.md

@@ -3,6 +3,16 @@
 This repository contains both the content and the static-site generator code for the
 Prometheus documentation site.
 
+## Contributing Changes
+
+See [`CONTRIBUTING.md`](CONTRIBUTING.md) for general instructions for new Prometheus contributors.
+
+The main documentation contents of this website are located in the [`content/docs`](content/docs) directory.
+
+Documentation concerning the Prometheus server is [maintained in the Prometheus server repository](https://github.com/prometheus/prometheus/tree/master/docs) and cloned into the website at build time.
+
+As a guideline, please keep the documentation generally applicable and avoid use-case-specific changes.
+
 ## Prerequisites
 
 You need to have a working Ruby environment set up and then install the

content/css/docs.css

@@ -398,6 +398,14 @@ footer {
   margin-left: 0;
 }
 
+.doc-content .open-source-notice {
+  color: #666;
+  background-color: #f5f5f5;
+  text-align: center;
+  padding: 0.8em;
+  margin-top: 1.5em;
+}
+
 .toc {
   padding: 1em;
   background-color: #f5f5f5;

layouts/docs.html

@@ -12,6 +12,9 @@
 
     <div class="col-md-9 doc-content">
       <%= yield %>
+      <p class="open-source-notice">
+          <i class="fa fa-file"></i> This documentation is <a href="https://github.com/prometheus/docs#contributing-changes">open-source</a>. Please help improve it by filing issues or pull requests.
+      </p>
     </div>
 
   </div>