feat(examples): implicit MAML omniglot example

[Benjamin-eecs]

Description

Add implicit MAML omniglot example

Motivation and Context

To test implicit differetiation API

Checklist

Go over all the following points, and put an x in all the boxes that apply. If you are unsure about any of these, don't hesitate to ask. We are here to help!

• [x] I have read the CONTRIBUTION guide (required)
• [x] I have reformatted the code using make format (required)
• [x] I have checked the code using make lint (required)
• [x] I have ensured make test pass. (required)

[codecov-commenter]

Codecov Report

Base: 63.16% // Head: 63.30% // Increases project coverage by +0.14% :tada:

Coverage data is based on head (d280559) compared to base (6604625). Patch coverage: 92.10% of modified lines in pull request are covered.

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #48      +/-   ##
==========================================
+ Coverage   63.16%   63.30%   +0.14%     
==========================================
  Files          58       58              
  Lines        2302     2303       +1     
==========================================
+ Hits         1454     1458       +4     
+ Misses        848      845       -3     

Flag	Coverage Δ
unittests	63.30% <92.10%> (+0.14%)	:arrow_up:

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
torchopt/diff/implicit/decorator.py	94.39% <91.89%> (+1.40%)	:arrow_up:
torchopt/typing.py	95.83% <100.00%> (+0.18%)	:arrow_up:

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