message: Fix links for mkdocs/relative
diff: @@ -48,8 +48,8 @@ source candidates. (And we'll probably end up writing some brand new ones, too.)
  ### What's the roadmap for Backstage?
  We envision three phases, which you can learn about in
  -[our project roadmap](overview/roadmap). Even though the open source version of
  -Backstage is relatively new compared to our internal version, we have already
  +[our project roadmap](overview/roadmap.md). Even though the open source version
  +of Backstage is relatively new compared to our internal version, we have already
  begun work on various aspects of all three phases. Looking at the
  [milestones for active issues](https://github.com/backstage/backstage/milestones)
  will also give you a sense of our progress.
  @@ -114,7 +114,7 @@ type of content. Plugins all use a common set of platform APIs and reusable UI
  components. Plugins can fetch data either from the backend or an API exposed
  through the proxy.
  -Learn more about [the different components](overview/what-is-backstage) that
  +Learn more about [the different components](overview/what-is-backstage.md) that
  make up Backstage.
  ### Do I have to write plugins in TypeScript?
  @@ -217,9 +217,9 @@ data is shared with.
  Yes. The core frontend framework could be used for building any large-scale web
  application where (1) multiple teams are building separate parts of the app, and
  (2) you want the overall experience to be consistent. That being said, in
  -[Phase 2](overview/roadmap) of the project we will add features that are needed
  -for developer portals and systems for managing software ecosystems. Our ambition
  -will be to keep Backstage modular.
  +[Phase 2](overview/roadmap.md) of the project we will add features that are
  +needed for developer portals and systems for managing software ecosystems. Our
  +ambition will be to keep Backstage modular.
  ### How can I get involved?
  