feat: add rotated linknet_resnet18 tensorflow ckpts

[charlesmindee]

Following #816, this PR adds the checkpoints of the trained linket_resnet18 on rotated samples.
Any feedback is welcome!

[codecov]

Codecov Report

Merging #817 (1adf93e) into main (0310d6c) will decrease coverage by 0.29%.
The diff coverage is 86.46%.

@@            Coverage Diff             @@
##             main     #817      +/-   ##
==========================================
- Coverage   95.99%   95.69%   -0.30%     
==========================================
  Files         131      133       +2     
  Lines        5042     5133      +91     
==========================================
+ Hits         4840     4912      +72     
- Misses        202      221      +19     

Flag	Coverage Δ
unittests	95.69% <86.46%> (-0.30%)	⬇️

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

Impacted Files	Coverage Δ
doctr/models/zoo.py	100.00% <ø> (ø)
doctr/models/predictor/base.py	81.81% <53.84%> (-18.19%)	⬇️
doctr/models/detection/linknet/tensorflow.py	96.59% <66.66%> (-1.09%)	⬇️
doctr/transforms/modules/pytorch.py	94.52% <84.61%> (-3.79%)	⬇️
doctr/transforms/modules/tensorflow.py	92.90% <90.90%> (-0.16%)	⬇️
doctr/transforms/functional/base.py	95.65% <95.23%> (+1.90%)	⬆️
doctr/io/pdf.py	100.00% <100.00%> (+1.66%)	⬆️
doctr/io/reader.py	100.00% <100.00%> (ø)
doctr/models/detection/linknet/base.py	88.79% <100.00%> (ø)
doctr/models/detection/zoo.py	96.00% <100.00%> (ø)
... and 11 more

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[fg-mindee]

There are conflicts to be resolved if we are to move forward with the PR :)

[fg-mindee]

ping @charlesmindee :)

[fg-mindee]

With the recent changes on the loss, I think there has some conflicts to resolve before moving on with this!

[fg-mindee]

isort isn't happy but the rest is good 👍

[fg-mindee]

Thanks!