doc: update install doc to link to caching section (#31046)

Author: florianduros

docs/install.md

@@ -11,7 +11,7 @@ There are some exceptions like when using localhost, which is considered a [secu
 1. Download the latest version from <https://github.com/element-hq/element-web/releases>
 1. Untar the tarball on your web server
 1. Move (or symlink) the `element-x.x.x` directory to an appropriate name
-1. Configure the correct caching headers in your webserver (see below)
+1. Configure the correct caching headers in your webserver (see [README.md](../README.md#caching-requirements))
 1. Configure the app by copying `config.sample.json` to `config.json` and
    modifying it. See the [configuration docs](config.md) for details.
 1. Enter the URL into your browser and log into Element!