[Project] Add example project

[Ben-Louis]

Motivation

Modification

1. add readme for projects
2. add an example project in which a head and a loss are customized
3. add readme for example project

BC-breaking (Optional)

Use cases (Optional)

Checklist

Before PR:

• I have read and followed the workflow indicated in the CONTRIBUTING.md to create this PR.
• Pre-commit or linting tools indicated in CONTRIBUTING.md are used to fix the potential lint issues.
• Bug fixes are covered by unit tests, the case that causes the bug should be added in the unit tests.
• New functionalities are covered by complete unit tests. If not, please add more unit tests to ensure correctness.
• The documentation has been modified accordingly, including docstring or example tutorials.

After PR:

• CLA has been signed and all committers have signed the CLA in this PR.

[codecov]

Codecov Report

Base: 80.31% // Head: 80.19% // Decreases project coverage by -0.12% ⚠️

Coverage data is based on head (d1e94d8) compared to base (1941428).
Patch has no changes to coverable lines.

Additional details and impacted files

@@             Coverage Diff             @@
##           dev-1.x    #1914      +/-   ##
===========================================
- Coverage    80.31%   80.19%   -0.13%     
===========================================
  Files          209      209              
  Lines        12449    12417      -32     
  Branches      2100     2100              
===========================================
- Hits          9999     9958      -41     
- Misses        2003     2010       +7     
- Partials       447      449       +2     

Flag	Coverage Δ
unittests	80.19% <ø> (-0.13%)	⬇️

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

Impacted Files	Coverage Δ
mmpose/codecs/associative_embedding.py	92.50% <0.00%> (-3.75%)	⬇️
mmpose/models/pose_estimators/base.py	78.78% <0.00%> (-1.22%)	⬇️
mmpose/codecs/base.py	91.66% <0.00%> (-1.20%)	⬇️
mmpose/datasets/transforms/common_transforms.py	84.75% <0.00%> (-1.05%)	⬇️
mmpose/models/utils/regularizations.py	75.86% <0.00%> (-0.81%)	⬇️
mmpose/structures/pose_data_sample.py	97.05% <0.00%> (-0.67%)	⬇️
mmpose/apis/webcam/nodes/node.py	48.09% <0.00%> (-0.40%)	⬇️
mmpose/structures/multilevel_pixel_data.py	59.82% <0.00%> (-0.36%)	⬇️
mmpose/models/heads/base_head.py	83.87% <0.00%> (-0.26%)	⬇️
mmpose/datasets/transforms/bottomup_transforms.py	79.65% <0.00%> (-0.24%)	⬇️
... and 5 more

Help us with your feedback. Take ten seconds to tell us how you rate us. Have a feature suggestion? Share it here.

☔ View full report at Codecov.
📢 Do you have feedback about the report comment? Let us know in this issue.

[ly015]

Should be 1.x documentation

[Ben-Louis]

This part of doc has not been added in 1.x. The URL for Model section in Migration is used here as an alternative in the latest commit