fixes links (html => md)

doc/user/project/pages/getting_started_part_one.md

@@ -73,7 +73,7 @@ Pages wildcard domain. This guide is valid for any GitLab instance,
 you just need to replace Pages wildcard domain on GitLab.com
 (`*.gitlab.io`) with your own.
 
-Learn more about [namespaces](../../group/index.html#namespaces).
+Learn more about [namespaces](../../group/index.md#namespaces).
 
 ### Practical examples
 

doc/user/project/pages/getting_started_part_three.md

 # GitLab Pages from A to Z: Part 3
 
-> **Article [Type](../../../development/writing_documentation.html#types-of-technical-articles)**: user guide || 
+> **[Article Type](../../../development/writing_documentation.md#types-of-technical-articles)**: user guide || 
 > **Level**: beginner || 
 > **Author**: [Marcia Ramos](https://gitlab.com/marcia) ||
 > **Publication date:** 2017/02/22

doc/user/project/pages/introduction.md

@@ -400,7 +400,7 @@ If you are using GitLab.com to host your website, then:
 
 The rest of the guide still applies.
 
-See also: [GitLab Pages from A to Z: Part 1 - Static sites and GitLab Pages domains](getting_started_part_one.html#gitlab-pages-domain).
+See also: [GitLab Pages from A to Z: Part 1 - Static sites and GitLab Pages domains](getting_started_part_one.md#gitlab-pages-domain).
 
 ## Limitations