### What this PR does / why we need it?
add long_sequence feature user guide
- vLLM version: release/v0.13.0
- vLLM main:
bc0a5a0c08
---------
Signed-off-by: LookAround <lixushi@huawei.com>
### What this PR does / why we need it?
add long_sequence feature user guide
- vLLM version: release/v0.13.0
- vLLM main:
bc0a5a0c08
---------
Signed-off-by: LookAround <lixushi@huawei.com>