docs/integration: add Java

This adds a Java card to the integrations index, prominently marked as a
technology preview.

The card links to the "getting started with CUE in Java" tutorial, to
avoid writing a separate "how CUE work with Java" concept guide. This
would be needed to mirror the other integrations cards' links, but
wouldn't (currently) add much content beyond that which is included by
tutorial.

Fixes cue-lang/docs-and-content#175

Preview-Path: /docs/integration/
Signed-off-by: Jonathan Matthews <[email protected]>
Change-Id: Ieb2fb97567c3f8efb00fcdeaa55beeecf4905a32
Reviewed-on: https://review.gerrithub.io/c/cue-lang/cuelang.org/+/1199335
TryBot-Result: CUEcueckoo <[email protected]>
Reviewed-by: Daniel Martí <[email protected]>

content/docs/integration/_en.md

@@ -74,6 +74,17 @@ CUE understands **JSON Schema constraints** through its Go API and the `cue`
 command, enabling schemas to be used to constrain and validate data directly,
 and to be expressed in other formats - including CUE.
 {{< /card >}}
+
+{{< card
+    title="Java"
+    href="/docs/tutorial/get-started-cue-java/"
+    label="Learn more"
+>}}{{< sidenote text="Technology preview">}}
+
+Support for using CUE in Java is available through an experimental Java library.
+
+Follow this introductory tutorial to get started with CUE in Java.
+{{< /card >}}
 {{< /cards >}}
 
 ## Technologies

hugo/content/en/docs/integration/_index.md

@@ -74,6 +74,17 @@ CUE understands **JSON Schema constraints** through its Go API and the `cue`
 command, enabling schemas to be used to constrain and validate data directly,
 and to be expressed in other formats - including CUE.
 {{< /card >}}
+
+{{< card
+    title="Java"
+    href="/docs/tutorial/get-started-cue-java/"
+    label="Learn more"
+>}}{{< sidenote text="Technology preview">}}
+
+Support for using CUE in Java is available through an experimental Java library.
+
+Follow this introductory tutorial to get started with CUE in Java.
+{{< /card >}}
 {{< /cards >}}
 
 ## Technologies