regex: add page (#19617)

Co-authored-by: Managor <42655600+Managor@users.noreply.github.com>

pages/common/regex.md

@@ -0,0 +1,33 @@
+# regex
+
+> Regular expressions (`regex`) are patterns used to match, search, and manipulate text.
+> Not a direct command, but syntax to be used with other commands.
+> More information: <https://cheatography.com/davechild/cheat-sheets/regular-expressions/>.
+
+- Match any single character:
+
+`.`
+
+- Match the start of a line:
+
+`^{{hello}}`
+
+- Match the end of a line:
+
+`{{world}}$`
+
+- Match zero or more repeated characters:
+
+`{{a}}*`
+
+- Match a set of characters:
+
+`[{{abc}}]`
+
+- Match a range of characters:
+
+`[{{a-z3-9}}]`
+
+- Match anything but the specified character:
+
+`[^{{a}}]`