Added documentation for NGINX Unit process defaults

Author: jaydrogers

docs/content/docs/7.reference/1.environment-variable-specification.md

@@ -68,4 +68,7 @@ We like to customize our images on a per app basis using environment variables.
 `UNIT_CERTIFICATE_NAME`<br />*Default: "self-signed-web-bundle"*| Name of your certificate bundle. This is used to configure HTTPS. (<a target="_blank" href="https://unit.nginx.org/configuration/#ssl-tls-configuration">Official Docs</a>)| unit
 `UNIT_CONFIG_DIRECTORY`<br />*Default: "/etc/unit/config.d"*|Path to the Unit configuration directory. Any *.json, *.js, and *.pem files will be loaded into Unit on initialization.| unit
 `UNIT_CONFIG_FILE`<br />*Default: "/etc/unit/config.d/config.json"*|Path to the Unit configuration file. One will be generated automatically by default. (<a target="_blank" href="https://unit.nginx.org/configuration/#">Official Docs</a>)| unit
+`UNIT_PROCCESSES_IDLE_TIMEOUT`<br />*Default: "30"*|The maximum time in seconds that an idle process will be kept alive. (<a target="_blank" href="https://unit.nginx.org/configuration/#application-processes">Official Docs</a>)| unit
+`UNIT_PROCCESSES_MAX`<br />*Default: "20"*|The maximum number of application processes that can be started. (<a target="_blank" href="https://unit.nginx.org/configuration/#application-processes">Official Docs</a>)| unit
+`UNIT_PROCCESSES_SPARE`<br />*Default: "5"*|Minimum number of idle processes that Unit tries to maintain for an app. (<a target="_blank" href="https://unit.nginx.org/configuration/#application-processes">Official Docs</a>)| unit
 `UNIT_WEBROOT`<br />*Default: "/var/www/html/public"*|Base directory of the app’s file structure. All URI paths are relative to it. (<a target="_blank" href="https://unit.nginx.org/configuration/#php">Official Docs</a>)| unit