Extend grid view to the right to better fill the page

- Use a negative right margin to pull `.grid__wrapper` into the dead space left for a sidebar.
- Add sample documents to "portfolio" collection to test grid view
- Update CHANGELOG and history

CHANGELOG.md

@@ -7,6 +7,7 @@
 - Improve `page` and `archive` layouts to visually center main content and harmonize sidebar widths and placement. [#1166](https://github.com/mmistakes/minimal-mistakes/pull/1166)
 - Increase font-size of code blocks.
 - Reduce indent of nested "table of contents" links.
+- Extend [archive grid view](https://mmistakes.github.io/minimal-mistakes/docs/layouts/) to the right to better fill the page.
 
 ## Bug Fixes
 
@@ -18,6 +19,7 @@
 - Fix typo `words_per_minute` typo in documentation. [#1164](https://github.com/mmistakes/minimal-mistakes/pull/1164)
 - Remove outside and right borders in `table`s.
 - Adjust width of `.sidebar` to match `.sidebar__right`.
+- Add sample documents to ["portfolio" collection](https://mmistakes.github.io/minimal-mistakes/portfolio/) for testing grid view.
 
 ## [4.5.0](https://github.com/mmistakes/minimal-mistakes/releases/tag/4.5.0)