docs/concept: reword concept guide index page

This updates the prose on /docs/concept/ to include an in-page pointer
to the popular-guides page to steer the newcomer more readily towards
that hand-picked list, and tightens up the wording that preceeds the
in-page search UI.

It also promotes the Modules concept guide to be persistently linked
from the concept guide hierarchy's left-hand nav index, befitting the
feature's important role in CUE schema and data sharing. The modules
concept guide's title has its leading "CUE" removed as it presents oddly
on the page.

Preview-Path: /docs/concept/
Preview-Path: /docs/concept/modules/
Signed-off-by: Jonathan Matthews <[email protected]>
Change-Id: I07f13c04c73d880247c98295e630e7068ff39cb6
Dispatch-Trailer: {"type":"trybot","CL":1202869,"patchset":4,"ref":"refs/changes/69/1202869/4","targetBranch":"master"}

content/docs/concept/_en.md

@@ -12,8 +12,9 @@ They explore the foundations and implications of CUE's theoretical basis in
 depth, and provide background information to help the CUE user discover how
 best to take advantage of its unique and powerful features.
 
-Use this interface to browse and search through the contents, titles, examples,
-and tags of the guides, and to narrow down the list of guides to a specific
-topic:
+The [Popular guides]({{< relref "popular-guides" >}}) page contains a curated
+list of concept guides.
+You can also use the following index to browse through the full range of concept guides,
+or to search inside them for specific content, titles, and tags:
 
 {{< search contentType="Concept Guides" showContentTypes=false >}}

content/docs/concept/modules/_en.md

@@ -1,7 +1,7 @@
 ---
-title: CUE Modules
+title: Modules
 tags: [modules]
-toc_hide: true
+toc_hide: false
 ---
 
 Modules are how CUE manages native dependencies.

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

@@ -12,8 +12,9 @@ They explore the foundations and implications of CUE's theoretical basis in
 depth, and provide background information to help the CUE user discover how
 best to take advantage of its unique and powerful features.
 
-Use this interface to browse and search through the contents, titles, examples,
-and tags of the guides, and to narrow down the list of guides to a specific
-topic:
+The [Popular guides]({{< relref "popular-guides" >}}) page contains a curated
+list of concept guides.
+You can also use the following index to browse through the full range of concept guides,
+or to search inside them for specific content, titles, and tags:
 
 {{< search contentType="Concept Guides" showContentTypes=false >}}

hugo/content/en/docs/concept/modules/_index.md

@@ -1,7 +1,7 @@
 ---
-title: CUE Modules
+title: Modules
 tags: [modules]
-toc_hide: true
+toc_hide: false
 ---
 
 Modules are how CUE manages native dependencies.