Fix vertical alignment in single page and error layouts (#2114)

Co-authored-by: Paweł Kuna <1282324+codecalm@users.noreply.github.com>
Co-authored-by: codecalm <codecalm@gmail.com>

.changeset/smart-fans-pump.md

@@ -0,0 +1,5 @@
+---
+"@tabler/core": patch
+---
+
+Fix vertical alignment in single page and error layouts

preview/pages/_layouts/error.html

@@ -1,9 +1,9 @@
 ---
 layout: base
-body-class: border-top-wide border-primary d-flex flex-column
+body-class: border-top-wide border-primary
 ---
 
-<div class="page justify-content-center">
+<div class="page page-center">
 	<div class="container-tight py-4">
 		{% assign error = errors[page-error] %}
 		{% assign header = error.header | default: 'Oops… You just found an error page' %}

preview/pages/_layouts/single.html

@@ -1,9 +1,8 @@
 ---
 layout: base
-body-class: d-flex flex-column
 ---
 
-<div class="page">
+<div class="page page-center">
 	<div class="container container-{{ container-size | default: 'tight' }} py-4">
 		{% unless hide-logo %}
 		<div class="text-center mb-4">