Add roadmap board link to Roadmaps page (napari#212)

# Description

Adds link to GitHub board containing the napari roadmap to Roadmap page.

EDIT: [Rendered page is
here](https://output.circle-artifacts.com/output/job/31a35d46-3a9c-414e-ad63-7f7a8a988b93/artifacts/0/docs/_build/roadmaps/index.html)

## Type of change
- [x] Fixes or improves existing content

# References
Closes napari#182 

## Final checklist:
- [x] My PR is the minimum possible work for the desired functionality

docs/developers/contributing.md

@@ -5,6 +5,8 @@ We welcome your contributions! Please see the provided steps below and never hes
 
 If you are a new user, we recommend checking out the detailed [Github Docs](https://docs.github.com/en).
 
+You can see the general direction for napari development and possible work plans in our current [Roadmap](../roadmaps/index.md).
+
 (dev-installation)=
 ## Setting up a development installation
 

docs/developers/index.md

@@ -2,6 +2,8 @@
 
 Here you can find resources about the contributing workflow for both code to napari core and documentation of the project, as well as information for onboarding of new core developers.
 
+You can see the general direction for napari development and possible work plans in our current [Roadmap](../roadmaps/index.md).
+
 ## For contributors
 
 - [Contributing guide](./contributing)

docs/roadmaps/index.md

@@ -1,3 +1,13 @@
 # Roadmaps
 
-Past and future roadmaps for the `napari` project.
+The current `napari` roadmap can be seen in the following GitHub board: [napari global roadmap](https://github.com/orgs/napari/projects/24/views/2?pane=info)
+
+This roadmap captures the current priorities of the napari core developer team. It is revisited every six months.
+
+---
+
+You can see past roadmaps below.
+
+- [](0_4.md)
+- [](0_3_retrospective.md)
+- [](0_3.md)