Support \frametitle in outline

[tfardet]

Steps to Reproduce

Use the default template shown in the overleaf introduction to beamer, the frame title does not appear in the outline in the left navbar.

1. Copy paste the code in the introduction to beamer
2. Check that "Sample frame title" does not appear in the outline on the left navbar (bottom)
3. Replace \frametitle by \begin{frame}{Sample frame title} and "Sample frame title" appears in the outline

Expected Behaviour

"Sample frame title" should appear in the outline also for \frametitle.

Observed Behaviour

The frame title does not appear in the outline with \frametitle.

Context

I work with people who took the habit of using \frametitle because of Overleaf's introduction and this makes navigating the presentation much more complicated.