[Feature] Add basic tutorial for SR models

[ckkelvinchan]

Motivation

A demo teaching users how to train and test existing models could help them get familiar with MMEditing.

Modification

This PR adds a basic tutorial for SR models. It includes both image and video SR models.

Remarks

There is a link to the comprehensive models, but the link hasn't been added.

[ckkelvinchan]

Please feel free to leave comments :)

[codecov]

Codecov Report

Merging #380 (4e5cb43) into master (7328829) will decrease coverage by 0.02%.
The diff coverage is n/a.

❗ Current head 4e5cb43 differs from pull request most recent head 8444e5f. Consider uploading reports for the commit 8444e5f to get more accurate results

@@            Coverage Diff             @@
##           master     #380      +/-   ##
==========================================
- Coverage   80.44%   80.42%   -0.03%     
==========================================
  Files         185      185              
  Lines        9889     9889              
  Branches     1441     1441              
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- Hits         7955     7953       -2     
- Misses       1742     1743       +1     
- Partials      192      193       +1     

Flag	Coverage Δ
unittests	80.41% <ø> (-0.02%)	⬇️

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Impacted Files	Coverage Δ
...ls/components/stylegan2/generator_discriminator.py	84.93% <0.00%> (-1.21%)	⬇️

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[innerlee]

See the installation step here https://github.com/open-mmlab/mmocr/blob/main/demo/MMOCR_Tutorial.ipynb
The mmcv-full is generally installed manually

edit:
also add a colab badge as in the above file. Try to run the whole file in colab to make sure it can run there

[ckkelvinchan]

See the installation step here https://github.com/open-mmlab/mmocr/blob/main/demo/MMOCR_Tutorial.ipynb
The mmcv-full is generally installed manually

edit:
also add a colab badge as in the above file. Try to run the whole file in colab to make sure it can run there

Note that the cell training and testing on pre-defined datasets are not expected to be run. It is used as a demo showing users how to use the command.

[ckkelvinchan]

It has been tested on colab.

[innerlee]

The file cannot be displayed by github. Please check if the format is correct.

Rebase master btw :)