Improve / patch UV installation steps

[marksverdhei]

As I'm locally installing blt using uv, I noticed a minor inconvenience that I think could and should be improved.
The original installation steps are incomplete because uv run will fail if you have not run uv sync first.

uv pip install --group pre_build --no-build-isolation
uv pip install --group compile_xformers --no-build-isolation
uv sync
uv run python download_blt_weights.py
uv run python demo.py "A BLT has"

And uv sync will fail because the groups are not installed under the right flags.
I suggest using this oneliner that passes no isolation groups as arguments to uv sync instead,
making the installation experience smoother.

uv sync --no-build-isolation-package pre_build --no-build-isolation-package compile_xformers
uv run python download_blt_weights.py
uv run python demo.py "A BLT has"

Tested on uv 0.7.21

Cheers