Added "Duplicated text" as a sufficient technique to fulfill the 1.4.5 Images of Text success criterion in the Understanding Document

[giacomo-petri]

Closes: #3755

This is a proposal to include "duplicated text" as a sufficient technique to satisfy the 1.4.5 Success Criterion, addressing users needs to personalize text presentation while also ensuring sustainability for companies (as entirely replacing text images with real text often results in inaction).

Updates:

• Included a section in the understanding document to consider this approach.
• Provided an example.
• Introduced a sufficient technique.