Add error message when `{{< include >}}` is used in invalid position

Bug description

I would like to use "include" to generate a list with info I will use across the document.
The rendering, however, is an empty bullet.

Example:

Assume the file warehousing_course_ilo_explain.qmd has the content ILO1.

Then, the following:

Upon finishing the MSc Warehousing course, students will be able to:

- {{< include warehousing_course_ilo_explain.qmd >}}

{{< include warehousing_course_ilo_explain.qmd >}}

Results:

Upon finishing the MSc Warehousing course, students will be able to:

ILO1

The bug happens both in Windows and Linux (WSL) + VS Code.

Checklist

• Please include a minimal, fully reproducible example in a single .qmd file? Please provide the whole file rather than the snippet you believe is causing the issue.
• Please format your issue so it is easier for us to read the bug report.
• Please document the RStudio IDE version you're running (if applicable), by providing the value displayed in the "About RStudio" main menu dialog?
• Please document the operating system you're running. If on Linux, please provide the specific distribution.