"Scope" attribute missing for #stepsContainer table headers

Tested on XWiki 10.8

AFFECTS:

• xwiki:Tour.HomepageTour.WebHome
• xwiki:TourCode.StepsListing
• xwiki:TourCode.TourSheet
• xwiki:TourCode.TourTemplate

ERROR:

• org.xwiki.test.webstandards.CustomDutchWebGuidelinesValidationTest.Validating HTML5 Dutch Web Guidelines validity for: xwiki:Tour.HomepageTour.WebHome executed with credentials Admin:admin (from org.xwiki.test.webstandards.AllTests)
• ERROR: <th> elements have been found that make no use the scope attribute. When scope is not used, be advised to use headers attributes and to use id attributes to associate table labels (<th> cells) with individual table cells (see R-pd.11.5).
• ERROR: No headers or id attributes have been found. When not using these be advised to use the scope attribute instead to associate table labels (<th> cells) with columns and rows. (see R-pd.11.4).

INVALIDATES:

• Dutch Guidelines: {{validateRpd11s4() validateRpd11s5() }}
  • https://github.com/xwiki/xwiki-platform/blob/master/xwiki-platform-tools/xwiki-platform-tool-standards-validator/src/main/java/org/xwiki/validator/DutchWebGuidelinesValidator.java#L1100
• R-pd.11.4 Use the scope attribute to associate table labels (th cells) with columns or rows.
• R-pd.11.5 Use the headers and id attributes to associate table labels (th cells) with individual cells in complex tables.

FIXES:

• Add scope attribute for th
• See possible values https://developer.mozilla.org/en-US/docs/Web/HTML/Element/th
• See examples https://www.w3.org/TR/WCAG20-TECHS/H63.html