Anchor generated plugin .gitgnore entries

This is a good practice to encourage to prevent inadvertent exclusions
from version control.  This also matches generated app .gitignore files.

Author: jonathanhefner

railties/lib/rails/generators/rails/plugin/templates/gitignore.tt

@@ -1,19 +1,19 @@
-.bundle/
-log/*.log
-pkg/
+/.bundle/
+/log/*.log
+/pkg/
 <% if with_dummy_app? -%>
 <% if sqlite3? -%>
-<%= dummy_path %>/db/*.sqlite3
-<%= dummy_path %>/db/*.sqlite3-*
+/<%= dummy_path %>/db/*.sqlite3
+/<%= dummy_path %>/db/*.sqlite3-*
 <% end -%>
-<%= dummy_path %>/log/*.log
+/<%= dummy_path %>/log/*.log
 <% unless options[:skip_javascript] -%>
-<%= dummy_path %>/node_modules/
-<%= dummy_path %>/yarn-error.log
+/<%= dummy_path %>/node_modules/
+/<%= dummy_path %>/yarn-error.log
 <% end -%>
 <% unless skip_active_storage? -%>
-<%= dummy_path %>/storage/
+/<%= dummy_path %>/storage/
 <% end -%>
-<%= dummy_path %>/tmp/
+/<%= dummy_path %>/tmp/
 <% end -%>
 .byebug_history