[DOC] Add header to cookie secret paragraph (#1025)

* [DOC] Add header to cookie secret paragraph

* Update overview.md

* Update overview.md

* Update overview.md

Co-authored-by: Joel Speed <Joel.speed@hotmail.co.uk>

docs/docs/configuration/overview.md

@@ -5,6 +5,8 @@ title: Overview
 
 `oauth2-proxy` can be configured via [config file](#config-file), [command line options](#command-line-options) or [environment variables](#environment-variables).
 
+### Generating a Cookie Secret
+
 To generate a strong cookie secret use `python -c 'import os,base64; print(base64.urlsafe_b64encode(os.urandom(16)).decode())'`
 
 ### Config File

docs/versioned_docs/version-6.1.x/configuration/overview.md

@@ -5,6 +5,8 @@ title: Overview
 
 `oauth2-proxy` can be configured via [config file](#config-file), [command line options](#command-line-options) or [environment variables](#environment-variables).
 
+### Generating a Cookie Secret
+
 To generate a strong cookie secret use `python -c 'import os,base64; print(base64.urlsafe_b64encode(os.urandom(16)).decode())'`
 
 ### Config File

docs/versioned_docs/version-7.0.x/configuration/overview.md

@@ -5,6 +5,8 @@ title: Overview
 
 `oauth2-proxy` can be configured via [config file](#config-file), [command line options](#command-line-options) or [environment variables](#environment-variables).
 
+### Generating a Cookie Secret
+
 To generate a strong cookie secret use `python -c 'import os,base64; print(base64.urlsafe_b64encode(os.urandom(16)).decode())'`
 
 ### Config File