【WIP】Document updating for next release.

[BalaBalaYi]

What changes were proposed in this pull request?

1. Complete the documentation for the new architecture.
2. Update the homepage.
3. Update release-related information.

Why are the changes needed?

Document updating for next main release: 0.6.0.

Does this PR introduce any user-facing change?

n/a

How was this patch tested?

n/a

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 80.27%. Comparing base (1543786) to head (b0f6dfb).

Additional details and impacted files

@@             Coverage Diff             @@
##           master    #1656       +/-   ##
===========================================
+ Coverage   69.77%   80.27%   +10.50%     
===========================================
  Files         228      228               
  Lines       22148    22225       +77     
===========================================
+ Hits        15454    17842     +2388     
+ Misses       6694     4383     -2311     

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