Minor update to dataset docs to lead users to quickstart and list_datasets

[DSGuala]

Context: Users have trouble finding all bondlength and basis combinations for qchem molecules. They end up using the slider on the website to check which bond lengths are available one-by-one.

Description of the Change:

• Updated the quickstart guide to say "viewing available datasets" instead of "dataset structure"
• Updated the qml.data docs to encourage users to first read the quickstart guide

Benefits: Users should be more likely to reach the list_datasets description in the quickstart guide and know that it can be used to view the available datasets.

Possible Drawbacks: Users who use pennylane.ai/datasets but don't go to the documentation still won't see this.

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[trbromley]

@DSGuala is this needed for the v0.36 release?

[DSGuala]

@DSGuala is this needed for the v0.36 release?

@trbromley Not required. We can leave it for the v0.37 release.

[josh146]

@DSGuala just to clarify, is this PR complete or did you still have changes you want to make? Because if it is complete, we could merge during feature freeze next week

[DSGuala]

@DSGuala just to clarify, is this PR complete or did you still have changes you want to make? Because if it is complete, we could merge during feature freeze next week

@josh146 this is basically completed. But I haven't had the bandwidth to take a final look or get it reviewed.

[trbromley]

@DSGuala would it make sense to come back to this now and get it merged in soon?

[DSGuala]

@DSGuala would it make sense to come back to this now and get it merged in soon?

Yup! I will take a look today.

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 99.66%. Comparing base (66421f1) to head (dac19a2). Report is 242 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #5484      +/-   ##
==========================================
- Coverage   99.67%   99.66%   -0.01%     
==========================================
  Files         422      422              
  Lines       40658    40362     -296     
==========================================
- Hits        40525    40228     -297     
- Misses        133      134       +1     

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