Prevent Firefox from using apple-touch-icon (#10402)

* Prevent Firefox from using apple-touch-icon

The opaque background does not work well in Firefox which uses the icon
as a "rich icon". Prevent this by not specifying it in HTML. Real Apple
devices will still request the icon on the static path.

Fixes: https://github.com/go-gitea/gitea/issues/10394

Also adjust gitignore so app.ini.sample becomes searchable and fixed a
variable name in app.ini.sample.

* fix gitignore

.gitignore

 
 /bin
 /dist
-/custom
+/custom/*
+!/custom/conf
+/custom/conf/*
+!/custom/conf/app.ini.sample
 /data
 /indexers
 /log

custom/conf/app.ini.sample

 PROTOCOL = http
 DOMAIN = localhost
 ROOT_URL = %(PROTOCOL)s://%(DOMAIN)s:%(HTTP_PORT)s/
-; when STATIC_URL_PREFIX is empty it will follow APP_URL
+; when STATIC_URL_PREFIX is empty it will follow ROOT_URL
 STATIC_URL_PREFIX =
 ; The address to listen on. Either a IPv4/IPv6 address or the path to a unix socket.
 HTTP_ADDR = 0.0.0.0

routers/routes/routes.go

 		}
 	})
 
+	m.Get("/apple-touch-icon.png", func(ctx *context.Context) {
+		ctx.Redirect(path.Join(setting.StaticURLPrefix, "img/apple-touch-icon.png"), 301)
+	})
+
 	// Progressive Web App
 	m.Get("/manifest.json", templates.JSONRenderer(), func(ctx *context.Context) {
 		ctx.HTML(200, "pwa/manifest_json")

templates/base/head.tmpl

 		};
 	</script>
 	<link rel="shortcut icon" href="{{StaticUrlPrefix}}/img/favicon.png">
-	<link rel="apple-touch-icon" href="{{StaticUrlPrefix}}/img/apple-touch-icon.png">
 	<link rel="mask-icon" href="{{StaticUrlPrefix}}/img/gitea-safari.svg" color="#609926">
 	<link rel="stylesheet" href="{{StaticUrlPrefix}}/vendor/assets/font-awesome/css/font-awesome.min.css">
 	<link rel="preload" as="font" href="{{StaticUrlPrefix}}/fomantic/themes/default/assets/fonts/icons.woff2" type="font/woff2" crossorigin="anonymous">