Update CHANGELOG and history

Author: mmistakes

CHANGELOG.md

@@ -1,3 +1,9 @@
+## Unreleased
+
+### Enhancements
+
+- Clarify documentation that Lunr only searches documents in collections. [#2450](https://github.com/mmistakes/minimal-mistakes/pull/2450)
+
 ## [4.19.1](https://github.com/mmistakes/minimal-mistakes/releases/tag/4.19.1)
 
 ### Enhancements

docs/_docs/18-history.md

@@ -5,10 +5,16 @@ permalink: /docs/history/
 excerpt: "Change log of enhancements and bug fixes made to the theme."
 sidebar:
   nav: docs
-last_modified_at: 2020-03-16T21:27:51-04:00
+last_modified_at: 2020-03-23T14:04:34-04:00
 toc: false
 ---
 
+## Unreleased
+
+### Enhancements
+
+- Clarify documentation that Lunr only searches documents in collections. [#2450](https://github.com/mmistakes/minimal-mistakes/pull/2450)
+
 ## [4.19.1](https://github.com/mmistakes/minimal-mistakes/releases/tag/4.19.1)
 
 ### Enhancements