docs/website/contribute.html: mention sponsoring opportunities

Include sponsoring the Buildroot Association, sponsoring in kind, and
sponsoring Buildroot LTS (through Mind).

This may create a somewhat muddled image so we may need to revisit in
the future how this is formulated.

Signed-off-by: Arnout Vandecappelle <arnout@mind.be>
Signed-off-by: Romain Naour <romain.naour@smile.fr>

docs/website/contribute.html

@@ -7,9 +7,9 @@
   <div class="panel panel-primary">
     <div class="panel-heading">Contribute</div>
     <div class="panel-body">
-      <p>Buildroot is an open source project and you are very welcome to contribute to
-	it.<br />
-	There are many different ways to contribute:</p>
+      <p>Buildroot is an open source project and we warmly welcome your
+        contributions.<br />
+	There are different ways you can get involved:</p>
 
       <ul>
 	<li>Reproducing, analyzing and fixing bugs from our
@@ -37,6 +37,30 @@
     </div>
   </div>
 
+  <div class="panel panel-primary">
+    <div class="panel-heading">Sponsor</div>
+    <div class="panel-body">
+      <p>Besides technical contributions, you can also support the project
+        financially.<br />
+	There are various ways make a financial contribution:</p>
+
+      <ul>
+	<li>Sponsor the <a href="./association.html">Buildroot Association</a>.
+	  The association helps Buildroot with infrastructure (servers, domain
+	  name, ...) and organising meetings. It relies on money from sponsors
+	  to organise those.</li>
+	<li>Practical help: providing a meeting room for developer meetings,
+	  providing autobuilder instances, etc.</li>
+	<li><a href="https://mind.be/buildroot-lts">Buildroot LTS Sponsoring</a>,
+	  a specific effort to finance the maintenance of the Long Term Support
+	  branch of Buildroot.</li>
+      </ul>
+
+      <p>All of these sponsors are thanked by listing them on the <a
+        href="./sponsors.html">sponsors page</a>.</p>
+    </div>
+  </div>
+
 </div><!--/.col-sm-10 -->
 </div><!--/.row -->
 </div>