Added title and brief for the new native extension pages

docs/en/manuals/extensions_best_practices.md

@@ -1,6 +1,11 @@
+---
+title: Native extensions - Best Practices
+brief: This manual describes best practices when developing native extensions.
+---
+
 # Best Practices
 
-Writing cross platform code can be difficult, but there are some ways to make it easier to both develop and maintain. In this document we list some ways we at Defold work with cross platform native code and API's.
+Writing cross platform code can be difficult, but there are some ways to make it easier to both develop and maintain. In this manual we list some ways we at Defold work with cross platform native code and API's.
 
 ## Defold code
 

docs/en/manuals/extensions_build_variants.md

@@ -1,3 +1,8 @@
+---
+title: Native extensions - Build variants
+brief: This manual describes the different builds variants that Defold can create and how they interact with native extensions and the engine.
+---
+
 # Native Extensions - Build Variants
 
 ## Build Variants

docs/en/manuals/extensions_details.md

@@ -1,3 +1,7 @@
+---
+title: Native extensions - Details
+brief: This manual describes some details about the build system used for native extensions.
+---
 
 # The Defold build setup
 
@@ -63,4 +67,3 @@ With it, we ship the libraries of the engine, and also a build manifest file,
 which is identical in structure and syntax as the [extension](/manuals/extensions_build_variants) and [app](/manuals/extensions_build_variants) manifests.
 
 (This sdk is not yet public)
-