build(bake): add cross-links to related topics

Signed-off-by: David Karlsson <35727626+dvdksn@users.noreply.github.com>

content/build/bake/_index.md

@@ -55,3 +55,7 @@ $ docker buildx bake
 
 This executes the `default` group, which builds the `frontend` and `backend`
 targets concurrently.
+
+## Get started
+
+To learn how to get started with Bake, head over to the [Bake introduction](./introduction.md).

content/build/bake/introduction.md

@@ -82,5 +82,10 @@ target "myapp" {
 }
 ```
 
-To see all the properties that can be set for a target, refer to the
-[Bake file reference](/build/bake/reference/).
+## Next steps
+
+To learn more about using Bake, see the following topics:
+
+- Learn how to define and use [targets](./targets.md) in Bake
+- To see all the properties that can be set for a target, refer to the
+  [Bake file reference](/build/bake/reference/).

content/build/bake/targets.md

@@ -93,3 +93,14 @@ command.
 ```console
 $ docker buildx bake all
 ```
+
+## Additional resources
+
+Refer to the following pages to learn more about Bake's features:
+
+- Learn how to use [variables](./variables.md) in Bake to make your build
+  configuration more flexible.
+- Learn how you can use matrices to build multiple images with different
+  configurations in [Matrices](./matrices.md).
+- Head to the [Bake file reference](/build/bake/reference/) to learn about all
+  the properties you can set in a Bake file, and its syntax.

content/build/bake/variables.md

@@ -124,3 +124,15 @@ $ docker buildx bake -f vars.hcl -f docker-bake.hcl --print app
   }
 }
 ```
+
+## Additional resources
+
+Here are some additional resources that show how you can use variables in Bake:
+
+- You can override `variable` values using environment variables. See
+  [Overriding configurations](./overrides.md#environment-variables) for more
+  information.
+- You can refer to and use global variables in functions. See [HCL
+  functions](./funcs.md#variables-in-functions)
+- You can use variable values when evaluating expressions. See [Expression
+  evaluation](./expressions.md#expressions-with-variables)