Auto merge of #28658 - mrl5:issue-28657, r=jdm

docs(linux): added runtime dependencies

Closes #28657

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added info about runtime dependencies needed for linux

---
<!-- Thank you for contributing to Servo! Please replace each `[ ]` by `[X]` when the step is complete, and replace `___` with appropriate data: -->
- [X] `./mach build -d` does not report any errors
- [X] `./mach test-tidy` does not report any errors
- [X] These changes fix #28657 (GitHub issue number if applicable)

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- [ ] There are tests for these changes OR
- [X] These changes do not require tests because it's a README change

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README.md

@@ -371,6 +371,14 @@ Run Servo with the command:
 - `Alt`+`right arrow` goes forwards in the history (`Cmd`+`right arrow` on Mac)
 - `Esc` or `Ctrl`+`Q` exits Servo (`Cmd`+`Q` on Mac)
 
+### Runtime dependencies
+
+#### Linux
+
+* `GStreamer` >=1.16
+* `gst-plugins-bad` >=1.16
+
+
 ## Developing
 
 There are lots of mach commands you can use. You can list them with `./mach