Add stactools.core.create.item

[gadomski]

Related Issue(s): #179

Description: This creates an item from a rasterio openable asset. The function tries to fill in as much data as possible from the rasterio dataset, but generally created items should be enhanced after creation with additional properties and STAC extensions.

Also includes a drop-dead simple command line interface.

PR checklist:

• Code is formatted (run scripts/format).
• Code lints properly (run scripts/lint).
• Tests pass (run scripts/test).
• Documentation has been updated to reflect changes, if applicable.
• Changes are added to the CHANGELOG.

[gadomski]

In #196 (comment) @kylebarron brought my attention to rio stac, which does more-or-less the same thing as this PR (with a slightly different approach). My initial instinct is to close this PR and recommend users favors rio stac, as it is (a) more feature-ful and (b) already extant, but I'd be curious whether @lossyrob, @cholmes, or others think it's worth having a "make an Item from an asset" functionality over here in stactools as well.

If this PR is closed, 7d74398 should be pulled out to its own PR.

[cholmes]

I'll let @lossyrob speak from the API perspective, but from a CLI perspective I think it makes good sense to include a 'create-item' command in the stac cli. If behind the scenes that uses rio stac directly I think that's fine / perhaps preferable for less code duplication. But I see stactools as the 'first' command line tool someone coming to STAC would use, and they might not know to install rio stac. But then there are also lots of rasterio users who may learn about stac from rio stac.

If it simplifies the code I could see stac create-item being really simple, but then also in its help / docs it'd point users at rio stac if they want more options.

[lossyrob]

If it simplifies the code I could see stac create-item being really simple, but then also in its help / docs it'd point users at rio stac if they want more options.

This seems like a good approach to me.