Update titles

Author: heitortsergent

docs/sources/k6/next/extensions/create/javascript-extensions.md

@@ -1,10 +1,10 @@
 ---
-title: 'JavaScript Extensions'
+title: 'JavaScript extensions'
 description: 'Follow these steps to build a JS extension for k6.'
 weight: 300
 ---
 
-# JavaScript Extensions
+# JavaScript extensions
 
 Take advantage of Go's speed, power, and efficiency while providing the flexibility of using JavaScript APIs
 within your test scripts.

docs/sources/k6/next/extensions/create/output-extensions.md

@@ -1,10 +1,10 @@
 ---
-title: 'Output Extensions'
+title: 'Output extensions'
 description: 'Follow these steps to build an output extension for k6.'
 weight: 400
 ---
 
-# Output Extensions
+# Output extensions
 
 k6 provides many [metrics](https://grafana.com/docs/k6/<K6_VERSION>/using-k6/metrics) and [output formats](https://grafana.com/docs/k6/<K6_VERSION>/results-output/), but it cannot directly support all possibilities.
 To store or alter metrics captured during an active k6 test,

docs/sources/k6/next/extensions/create/secret-source_extensions.md

@@ -1,10 +1,10 @@
 ---
-title: 'Secret source Extensions'
+title: 'Secret source extensions'
 description: 'Follow these steps to build an secret source extension for k6.'
 weight: 500
 ---
 
-# Secret Source Extensions
+# Secret Source extensions
 
 Secret source extension allow users to write or use written by other users extensions in order to get secrets to be used within k6 tests.