adds feature request template

[pablo-gar]

Adds an issue template for users providing a feature request.

[pablo-gar]

@atolopko-czi I'm assuming using quotes here will take care of the automated addition of the label "user request"

[codecov]

Codecov Report

Merging #302 (4b58f2d) into main (a927f72) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##             main     #302   +/-   ##
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  Coverage   91.54%   91.54%           
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  Files          41       41           
  Lines        2260     2260           
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  Hits         2069     2069           
  Misses        191      191           

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unittests	91.54% <ø> (ø)

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[atolopko-czi]

Some suggestions and a few corrections.

Also, see these templates, in case they're sufficient and we don't want to recreate the wheel:
*https://github.com/single-cell-data/TileDB-SOMA/blob/main/.github/ISSUE_TEMPLATE/feature_request.md

• https://github.com/chanzuckerberg/single-cell-explorer/blob/main/.github/ISSUE_TEMPLATE/---feature-request.md

[pablo-gar]

Thanks for your comments @pablo-gar I addressed them all. I inspired the template from the single-cell-data-portal template. I added one section based on the other templates.

I think this one is a slight improvement, unless you have any strong concerns about consistency then I'd prefer to keep it.