Add introductory paragraph to infrastructure description

Author: zklaus

docs/maintainer/infrastructure.md

@@ -4,6 +4,15 @@ title: 'Infrastructure'
 
 # Infrastructure
 
+This page gives an overview of the conda-forge infrastructure, that is, an account of the various pieces maintained by the conda-forge contributors as well as third-party providers that collectively form the basis for the operation of conda-forge.
+
+We start with the different Github [repositories](#repositories) maintained by conda-forge itself, then describe the administrative commands available for use in those repositories, the [Admin web services](#admin-web-services), followed by [the CI services](#ci-build-services), i.e. the third-party providers used for building and maintaining packages together.
+After that, we turn to a description of some aspects of the build environment for packages in [Compilers and Runtimes](#compilers-and-runtimes), together with [details about the upload to the package server](#output-validation-and-feedstock-tokens).
+
+[Then](#how-package-building-interacts-with-infrastructure), we see how the process of building a package interacts with different parts of the infrastructure.
+
+The following depiction of [automation](#automated-maintenance) explains what makes conda-forge a smoothly running machine.
+
 ## Repositories
 
 ### Staged-recipes