fix(text): add iframe to whitelist

[ThomasSevagen]

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• I have detailed the tests to do in my feature/fix in order to prevent consequents regressions (must specify in Checklist tests)
• I have performed a self-review of my code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation (API Doc etc...) - (must specify in Description for target version)
• If it is a consequent feature, I have added thorough tests.
• I have added tests that prove my fix is effective or that my feature works
• Any dependent changes have been added to this project (must specify in Description)