add release docs for 0.7.0

[github-actions[bot]]

:point_left: Launch a binder notebook on this branch for commit cf5a1f76bb8b4b9408a30cd23fa82b500006d8c5

I will automatically update this comment whenever this PR is modified

:point_left: Launch a binder notebook on this branch for commit 1ceae112db8f87af59d97736d1168869e4106e20

[codecov-commenter]

Codecov Report

Patch and project coverage have no change.

Comparison is base (ff2d49d) 59.12% compared to head (1ceae11) 59.12%.

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```diff @@ Coverage Diff @@ ## development #415 +/- ## ============================================ Coverage 59.12% 59.12% ============================================ Files 30 30 Lines 2263 2263 Branches 488 488 ============================================ Hits 1338 1338 Misses 842 842 Partials 83 83 ``` Help us with your feedback. Take ten seconds to tell us [how you rate us](https://about.codecov.io/nps?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=icesat2py). Have a feature suggestion? [Share it here.](https://app.codecov.io/gh/feedback/?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=icesat2py)

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