Check for correct semantic html elements

https://developer.mozilla.org/en-US/docs/Glossary/semantics

• correct usage of h1-h6 elements

added part::frontend type::refactoring labels

assigned to @ZugBahnHof

changed due date to June 11, 2021

created merge request !657 (merged) to address this issue

mentioned in merge request !657 (merged)

added board::ready label

closed with merge request !657 (merged)

mentioned in commit aa32d543