add mappings for CM3 data(enso)

[rhaegar325]

This PR add mappings for variables pr, ts, tauu in CM3 data.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 60.91%. Comparing base (0eb8d0e) to head (ba2260d).
⚠️ Report is 2 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #169      +/-   ##
==========================================
+ Coverage   52.02%   60.91%   +8.89%     
==========================================
  Files          18       18              
  Lines        2722     2848     +126     
==========================================
+ Hits         1416     1735     +319     
+ Misses       1306     1113     -193     

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