Add docs configuration

To allow rendering the track's documents on the v3 website, we're introducing a docs/config.json file.

This commit adds the docs/config.json file.

docs/config.json

@@ -0,0 +1,32 @@
+{
+  "docs": [
+    {
+      "uuid": "b1e7de5a-371d-4b11-b2f8-8bfc58b6eca8",
+      "slug": "installation",
+      "path": "docs/INSTALLATION.md",
+      "title": "Installing Crystal locally",
+      "blurb": "Learn how to install Crystal locally to solve Exercism's exercises on your own machine"
+    },
+    {
+      "uuid": "3ef9fe1c-43a0-43d0-b40d-56f39bf219ec",
+      "slug": "learning",
+      "path": "docs/LEARNING.md",
+      "title": "How to learn Crystal",
+      "blurb": "An overview of how to get started from scratch with Crystal"
+    },
+    {
+      "uuid": "c52b4d43-3a68-49d2-af37-e74e7e047df0",
+      "slug": "tests",
+      "path": "docs/TESTS.md",
+      "title": "Testing on the Crystal track",
+      "blurb": "Learn how to test your Crystal exercises on Exercism"
+    },
+    {
+      "uuid": "f8fe3ce0-9481-42dc-b8ba-a0e3dedb00db",
+      "slug": "resources",
+      "path": "docs/RESOURCES.md",
+      "title": "Useful Crystal resources",
+      "blurb": "A collection of useful resources to help you master Crystal"
+    }
+  ]
+}