Document ability to select directly from files in datafusion-cli

[alamb]

Which issue does this PR close?

re #4580

Rationale for this change

The feature added in #4838 is so cool -- we need to let our users know!

What changes are included in this PR?

Update datafusion-cli documentation

Are these changes tested?

N/A

Are there any user-facing changes?

Just docs

[jackwener]

Look great to me, thanks @alamb

[ursabot]

Benchmark runs are scheduled for baseline = 664edea and contender = 4bea81b. 4bea81b is a master commit associated with this PR. Results will be available as each benchmark for each run completes.
Conbench compare runs links:
[Skipped ⚠️ Benchmarking of arrow-datafusion-commits is not supported on ec2-t3-xlarge-us-east-2] ec2-t3-xlarge-us-east-2
[Skipped ⚠️ Benchmarking of arrow-datafusion-commits is not supported on test-mac-arm] test-mac-arm
[Skipped ⚠️ Benchmarking of arrow-datafusion-commits is not supported on ursa-i9-9960x] ursa-i9-9960x
[Skipped ⚠️ Benchmarking of arrow-datafusion-commits is not supported on ursa-thinkcentre-m75q] ursa-thinkcentre-m75q
Buildkite builds:
Supported benchmarks:
ec2-t3-xlarge-us-east-2: Supported benchmark langs: Python, R. Runs only benchmarks with cloud = True
test-mac-arm: Supported benchmark langs: C++, Python, R
ursa-i9-9960x: Supported benchmark langs: Python, R, JavaScript
ursa-thinkcentre-m75q: Supported benchmark langs: C++, Java