Improve object_store crate documentation

[alamb]

Which issue does this PR close?

Closes #2202

Rationale for this change

More docs == more better

What changes are included in this PR?

• Update main crate readme (What appears in https://crates.io/crates/object_store)
• Add main example (front page of https://docs.rs/object_store/latest/object_store/)

Example front page:

Are there any user-facing changes?

Better docs

[tustvold]

Minor nits, thank you for doing this

[tustvold]

Suggested change

	A focused, easy to use, idiomatic, high performance, `async` object
	store library interacting with object stores.
	A high performance, `async` object store crate that provides a
	uniform interface for interacting with various kinds of object store

I think all the qualifiers is a bit much 😆

[alamb]

I am practicing "marketing" -- I would like to run an experiment to see how much attention I can garner with a buzzword laden lead compared to a more utilitarian, less self-aggrandizing, summary.

[codecov-commenter]

Codecov Report

Merging #2260 (990f81b) into master (2c09ba4) will increase coverage by 0.00%.
The diff coverage is 100.00%.

❗ Current head 990f81b differs from pull request most recent head 88e2060. Consider uploading reports for the commit 88e2060 to get more accurate results

@@           Coverage Diff           @@
##           master    #2260   +/-   ##
=======================================
  Coverage   82.28%   82.28%           
=======================================
  Files         245      245           
  Lines       62670    62688   +18     
=======================================
+ Hits        51567    51585   +18     
  Misses      11103    11103           

Impacted Files	Coverage Δ
object_store/src/aws.rs	0.00% <ø> (ø)
object_store/src/azure.rs	0.00% <ø> (ø)
object_store/src/gcp.rs	0.00% <ø> (ø)
object_store/src/lib.rs	86.75% <ø> (ø)
arrow/src/datatypes/types.rs	97.93% <100.00%> (+0.46%)	⬆️
arrow/src/datatypes/datatype.rs	62.30% <0.00%> (-0.32%)	⬇️
parquet_derive/src/parquet_field.rs	65.98% <0.00%> (+0.22%)	⬆️

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[Ted-Jiang]

Nice write up! 😊

[alamb]

Thanks @Ted-Jiang !

[ursabot]

Benchmark runs are scheduled for baseline = 6bb4b5e and contender = 3e17891. 3e17891 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-rs-commits is not supported on ec2-t3-xlarge-us-east-2] ec2-t3-xlarge-us-east-2
[Skipped ⚠️ Benchmarking of arrow-rs-commits is not supported on test-mac-arm] test-mac-arm
[Skipped ⚠️ Benchmarking of arrow-rs-commits is not supported on ursa-i9-9960x] ursa-i9-9960x
[Skipped ⚠️ Benchmarking of arrow-rs-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