Enable standalone JavaScript plugins

The idea of 'standalone JavaScript plugins' came during the 'JavaScript
plugins' talk at the Gerrit User Summit.

The main concept is to automatically install and expose all *.js files
that are in Gerrit's plugins/ directory.  This should lower the entry
point barrier for JS developers.

There is one limitation of such plugins: they cannot contribute
additional resources.  When such are required, the implementer should
inline them in JS code or use the gerrit-plugin-js-archetype.

Change-Id: Ibad8c3938c0855fcabe6937fd8b4d508a9a2eac3
Signed-off-by: Dariusz Luksza <dariusz@luksza.org>

Documentation/dev-plugins.txt

diff --git a/Documentation/dev-plugins.txt b/Documentation/dev-plugins.txt
index 9459fb3..df14c1d 100644
--- a/Documentation/dev-plugins.txt
+++ b/Documentation/dev-plugins.txt
@@ -1704,9 +1704,13 @@
 Compiled plugins and extensions can be deployed to a running Gerrit
 server using the link:cmd-plugin-install.html[plugin install] command.
 
+WebUI plugins distributed as  single `.js` file can be deployed
+without the overhead of JAR packaging, for more information refer to
+link:cmd-plugin-install.html[plugin install] command.
+
 Plugins can also be copied directly into the server's
-directory at `$site_path/plugins/$name.jar`.  The name of
-the JAR file, minus the `.jar` extension, will be used as the
+directory at `$site_path/plugins/$name.(jar|js)`.  The name of
+the JAR file, minus the `.jar` or `.js` extension, will be used as the
 plugin name. Unless disabled, servers periodically scan this
 directory for updated plugins. The time can be adjusted by
 link:config-gerrit.html#plugins.checkFrequency[plugins.checkFrequency].