Add footer extra links template (#9576)

* Add footer extra links template

* [Docs] Update to mention extra links footer template

* Commit suggestion from @davidsvantesson

Co-Authored-By: David Svantesson <davidsvantesson@gmail.com>

* Move template placement to right side of footer

Co-authored-by: David Svantesson <davidsvantesson@gmail.com>
Co-authored-by: Lauris BH <lauris@nix.lv>

templates/base/footer_content.tmpl

@@ -19,6 +19,7 @@
 			<a href="{{StaticUrlPrefix}}/vendor/librejs.html" data-jslicense="1">JavaScript licenses</a>
 			{{if .EnableSwagger}}<a href="{{AppSubUrl}}/api/swagger">API</a>{{end}}
 			<a target="_blank" rel="noopener noreferrer" href="https://gitea.io">{{.i18n.Tr "website"}}</a>
+			{{template "custom/extra_links_footer" .}}
 			{{if (or .ShowFooterVersion .PageIsAdmin)}}<span class="version">{{GoVer}}</span>{{end}}
 		</div>
 	</div>