Feat imaging maps

[samaloney]

• Update demo to use images and create sunpy maps using the header helper.
• Fix ELUT lookup to use the corresponding science energy channels
• Small doc and docstring updates

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 68.92%. Comparing base (a35a42c) to head (6e8ddc7).

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #107 +/- ## ========================================== + Coverage 68.47% 68.92% +0.44% ========================================== Files 31 31 Lines 1843 1847 +4 ========================================== + Hits 1262 1273 +11 + Misses 581 574 -7 ```

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