[TASK] Apply new documentation standard definitions

This patch applies the new documentation standards to the .editorconfig.

Resolves: #97302
Releases: main, 11.5, 10.4
Change-Id: I798b355f71dfa7ba8ac20ad424105e99a5c870cc
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/74141


Tested-by: core-ci <typo3@b13.com>
Tested-by: Lina Wolf <112@linawolf.de>
Reviewed-by: Lina Wolf <112@linawolf.de>

.editorconfig

@@ -21,10 +21,14 @@ indent_size = 2
 indent_style = tab
 
 # ReST-Files
-[*.rst]
+[*.{rst,rst.txt}]
 indent_size = 4
 max_line_length = 80
 
+# Markdown-Files
+[*.md]
+max_line_length = 80
+
 # YAML-Files
 [*.{yaml,yml}]
 indent_size = 2