added links to docs (#5544)

sample.env

@@ -25,6 +25,7 @@ REDIS_URL=
 ### SMTP CONFIGURATION
 # Emails are required for the basic features of Greenlight to function.
 # Please refer to your SMTP provider to get the values for the variables below
+# More information: https://docs.bigbluebutton.org/greenlight/v3/install/#email-setup
 #SMTP_SENDER_EMAIL=
 #SMTP_SENDER_NAME=
 #SMTP_SERVER=
@@ -39,7 +40,7 @@ REDIS_URL=
 #SMTP_SSL_VERIFY=true
 
 ### EXTERNAL AUTHENTICATION METHODS
-#
+# More information: https://docs.bigbluebutton.org/greenlight/v3/install/#openid-connect-setup
 #OPENID_CONNECT_CLIENT_ID=
 #OPENID_CONNECT_CLIENT_SECRET=
 #OPENID_CONNECT_ISSUER=
@@ -47,6 +48,7 @@ REDIS_URL=
 #OPENID_CONNECT_UID_FIELD=
 
 # To enable hCaptcha on the user sign up and sign in, define these 2 keys
+# More information: https://docs.bigbluebutton.org/greenlight/v3/install/#hcaptcha-setup
 #HCAPTCHA_SITE_KEY=
 #HCAPTCHA_SECRET_KEY=
 
@@ -71,9 +73,11 @@ REDIS_URL=
 
 # Define the default locale language code (i.e. 'en' for English) from the following list:
 #  [en, ar, fr, es, fa_IR]
+# More information: https://docs.bigbluebutton.org/greenlight/v3/install/#default-locale-setup
 #DEFAULT_LOCALE=en
 
 # Set this if you like to deploy Greenlight on a relative root path other than /
+# More information: https://docs.bigbluebutton.org/greenlight/v3/install/#relative-url-root-path-subdirectory-setup
 #RELATIVE_URL_ROOT=/gl
 
 ## Define log level in production.