Add examples to extract scalar values in Flux doc

User would like more examples in the Extract scalar values in Flux doc:

" It would be nice if this page would contain examples which one can just execute. First step would be how to load the sample data used in that example and a table view of that sample data... loading the sample data as shown in the end and pasting the SFOTemps stuff brings up an error error in query specification while starting program: this Flux script returns no streaming data. Consider adding a "yield" or invoking streaming functions directly, without performing an assignment."

https://docs.influxdata.com/influxdb/v2.2/query-data/flux/scalar-values/

Start with the Extract scalar values in Flux page at the linked URL and review the existing SFOTemps example and sample-data loading instructions. Add executable examples that show how to load the sample data and display it as a table, and verify the resulting script produces streaming data without the reported yield error.

Written by the indexing model from the issue text.