Update Install guide with wget command for vllm-0.8.5

[Zhanli-Li]

Include the command to download the wheel directly before installation to prevent errors caused by missing wheels.

[muhammadyaseen]

Would be nice to also add a note that Python development dependencies may be required to run it:

sudo apt install python3-dev

Otherwise we'd encounter the following error:

/tmp/tmpsq39tlwt/main.c:5:10: fatal error: Python.h: No such file or directory
5 | #include <Python.h>
| ^~~~~~~~~~
compilation terminated.