[Docs] Add abstract and image for every paper.

[mzr1996]

Modification

Copy the abstract and main graph in every paper to the README.

Checklist

Before PR:

• Pre-commit or other linting tools are used to fix the potential lint issues.
• Bug fixes are fully covered by unit tests, the case that causes the bug should be added in the unit tests.
• The modification is covered by complete unit tests. If not, please add more unit test to ensure the correctness.
• The documentation has been modified accordingly, like docstring or example tutorials.

After PR:

• If the modification has potential influence on downstream or other related projects, this PR should be tested with those projects, like MMDet or MMSeg.
• CLA has been signed and all committers have signed the CLA in this PR.

[codecov]

Codecov Report

Merging #546 (6ad0585) into master (7977dc8) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #546   +/-   ##
=======================================
  Coverage   79.87%   79.87%           
=======================================
  Files         107      107           
  Lines        6093     6093           
  Branches      987      987           
=======================================
  Hits         4867     4867           
  Misses       1094     1094           
  Partials      132      132           

Flag	Coverage Δ
unittests	79.87% <ø> (ø)

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[Ezra-Yu]

LGTM.