[TASK] Add max_line_length to .editorconfig for rst files

The maximum line length of documentation files (80 characters)
should be reflected in the .editorconfig as described in
https://docs.typo3.org/m/typo3/docs-how-to-document/master/en-us/GeneralConventions/CodingGuidelines.html#line-length

Resolves: #90054
Releases: master, 9.5
Change-Id: Ib1c3f2f2fbae999b7d157949f1a59876c2ff451d
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/62818
Tested-by: TYPO3com <noreply@typo3.com>
Tested-by: Tymoteusz Motylewski <t.motylewski@gmail.com>
Tested-by: Benni Mack <benni@typo3.org>
Reviewed-by: Björn Jacob <bjoern.jacob@tritum.de>
Reviewed-by: Tymoteusz Motylewski <t.motylewski@gmail.com>
Reviewed-by: Benni Mack <benni@typo3.org>

.editorconfig

@@ -23,6 +23,7 @@ indent_style = tab
 # ReST-Files
 [*.rst]
 indent_size = 3
+max_line_length = 80
 
 # YAML-Files
 [*.{yaml,yml}]