Fix typo in site documentation for variables
Fixed "bellow" typo

Changed "bellow" to "below"
Merge pull request #2879 from SpectrumPixel/patch-1
Update history to reflect merge of #2879 [ci skip]
Merge pull request #2877 from nitoyon/fix-variables-doc
Update history to reflect merge of #2877 [ci skip]
Add the slugify Liquid filter
Add a test for the slugify Liquid filter
Document the slugify Liquid filter
Remove Good Include

The plugin is deprecated.
Merge pull request #2880 from kansaichris/slugify-liquid-filter
Update history to reflect merge of #2880 [ci skip]
Merge pull request #2881 from penibelst/patch-1
Update history to reflect merge of #2881 [ci skip]