Theme update (#553)

* Start to update the theme

- Ligther colors
- No more border radius
- Buttons are now always colored
- Start to redesign the post page (according to the Figma mockups)

* Fix build script: it now recompiles everytime a scss file changed

* Make sure the article illustrations are not too big

* Make articles wider (70 characters)

* Better contrast between gray shades

* Various improvements

* Better mobile style

* New style for the footer

* Improve comment style

* Better responsiveness again

* Limit the size of the article cover

* Last details?

- Improve buttons on the media page
- Improve lists

* Pin the stdweb version that we use

It changed because I removed Cargo.lock to handle a merge conflict

I could have updated cargo web too, but it mean I should have re-built
the CI docker image and it was taking forever.

* Better contrast for links in the header of the article

* Add a basic privacy policy

* Remove "also"

* Fix a few issues

- Don't watch static/css in build.rs
- Another shade of white
- Remove useless margin rule for error messages

templates/instance/about.rs.html

@@ -9,6 +9,8 @@
     <h1>@i18n!(ctx.1, "About {0}"; instance.name)</h1>
     <section>
     @Html(instance.short_description_html)
+
+    <p>@i18n!(ctx.1, "Runs Plume {0}"; env!("CARGO_PKG_VERSION"))</p>
     </section>
     <div class="banner">
         <section class="stats">
@@ -27,7 +29,6 @@
             <p><a href="@uri!(user::details: name = &admin.fqn)">@admin.name()</a><small>@@@admin.fqn</small></p>
         </div>
         </section>
-        <p>@i18n!(ctx.1, "Runs Plume {0}"; env!("CARGO_PKG_VERSION"))</p>
     </div>
     <section>
       @Html(instance.long_description_html)