Add HTML injections for markdown (#20527)

uncenter created

Closes https://github.com/zed-industries/extensions/issues/1588.

| Before | After |
| --- | --- |
| ![CleanShot 2024-11-11 at 22 48
43](https://github.com/user-attachments/assets/9470e6a8-6a37-4b8f-8daa-5c8c5ed2bb17)
| ![CleanShot 2024-11-11 at 22 49
43](https://github.com/user-attachments/assets/f2b858d0-9274-4332-b30e-61c13ac347c6)
|

Release Notes:

- Added HTML injections for markdown syntax highlighting

Change summary

crates/languages/src/markdown/injections.scm | 3 +++
1 file changed, 3 insertions(+)

Detailed changes