docs(sdk-metrics): add example of exponential histogram metric

[JamieDanielson]

Which problem is this PR solving?

Fixes #3852

Short description of the changes

• Adds example of Exponential Histogram metric to existing metric example app.
• Also adds a (commented-out) ConsoleMetricExporter for quick dev testing
• Updates a few typos while I was in the area

I didn't update the metrics.md with the specific example because that didn't seem to have all the specific examples; I will look to update the public website next though (opentelemetry.io)

Type of change

• Other; this is a documentation/example update

How Has This Been Tested?

• Run the example app with the ConsoleMetricExporter (comment out or don't use the OTLPMetricExporter) and see the example metric in the console. Run with debug to see all the extra datapoints

{
  descriptor: {
    name: 'test_exponential_histogram',
    description: 'Example of an ExponentialHistogram',
    type: 'HISTOGRAM',
    unit: '',
    valueType: 1
  },
  dataPointType: 1,
  dataPoints: [
    {
      attributes: [Object],
      startTime: [Array],
      endTime: [Array],
      value: [Object]
    }
  ]
}

Checklist:

• Followed the style guidelines of this project
• Unit tests have been added (N/A)
• Documentation has been updated (N/A)

[codecov]

Codecov Report

Merging #3855 (ee1b9d3) into main (6d13eb4) will not change coverage.
The diff coverage is n/a.

❗ Current head ee1b9d3 differs from pull request most recent head 8434869. Consider uploading reports for the commit 8434869 to get more accurate results

Additional details and impacted files

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[aabmass]

It's probably worth documenting that you can also achieve this for all histograms by setting this field on the metric reader:

opentelemetry-js/packages/sdk-metrics/src/export/MetricReader.ts

Line 42 in dfe6fe8

aggregationSelector?: AggregationSelector;

There is also an environment variable for this OTEL_EXPORTER_OTLP_METRICS_DEFAULT_HISTOGRAM_AGGREGATION but it doesn't look like it has been implemented yet (opened #3920)

[JamieDanielson]

Sorry all, I totally did a drive-by on this and forgot to come back to it. I committed the suggested change (forgot I changed that before pushing 😅 thank you).
I'll take a look at this again tomorrow and update accordingly.

[JamieDanielson]

Sorry for the slowness on this one! If this is good enough maybe we merge it in as-is and follow up with a better example/docs (along with the new env var implementation). I admittedly don't have a ton of experience with histograms 😅 so that is definitely adding to the bare bones of the example; was just hoping to get a little something in an example app.

[pichlermarc]

Thanks for adding this to the example 🙂

[pichlermarc]

This is great, thanks 🙂