qe: add doc on required postgres package for 2.1.0
ADD
quay-enterprise/installing-contributor-extensions-postgres.md
+# Installing Contributor Extensions for Postgres
+
+As of release 2.1.0 Quay Enterprise requires the [pg_trgm](https://www.postgresql.org/docs/current/static/pgtrgm.html) extension when using Postgres. This extension ships as part of the [Additional Supplied Modules](https://www.postgresql.org/docs/current/static/contrib.html). The requirements to allow extensions to be installed can be satisfied via package management tools on Debian and RedHat-based systems.
+
+## Debian/Ubuntu
+
+```
+# apt-get update
+# apt-get install postgresql-contrib -y
+```
+
+## Redhat/CentOS
+
+```
+# yum install postgresql-contrib
+```
+## Fedora
+
+```
+# dnf install postgresql-contrib
+```
+
+## Docker
+The [library/postgres](https://hub.docker.com/_/postgres/) container includes `postgresql-contrib` package by default.
+
+If using a container based on an OS above simply modify the Dockerfile to install `postgresql-contrib` package. If using an OS base that is not listed in may be required install `contrib` from [source](https://www.postgresql.org/docs/current/static/contrib.html).

qe: add doc on required postgres package for 2.1.0