Import Steam interactions (Australia subset)

[mdekstrand]

The Steam importer was not actually importing interactions (#1176). This fixes it to properly import interactions from the Australian subset of the data. Reviews and Full data are not yet supported.

Closes #1176.

[codecov]

Codecov Report

❌ Patch coverage is 92.85714% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 89.57%. Comparing base (1821af3) to head (96beabd).

Files with missing lines	Patch %	Lines
src/lenskit/data/sources/steam.py	92.85%	1 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1179   +/-   ##
=======================================
  Coverage   89.57%   89.57%           
=======================================
  Files         262      262           
  Lines       17405    17418   +13     
=======================================
+ Hits        15590    15603   +13     
  Misses       1815     1815           

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