SUBMARINE-1412. Add the missing 0.8.0 download page

[cdmikechen]

What is this PR for?

Add the missing 0.8.0 download file

What type of PR is it?

Hot Fix

Todos

• - 0.8.0 download page

What is the Jira issue?

https://issues.apache.org/jira/browse/SUBMARINE-1412

How should this be tested?

NA

Screenshots (if appropriate)

NA

Questions:

• Do the license files need updating? No
• Are there breaking changes for older versions? No
• Does this need new documentation? Yes

[codecov]

Codecov Report

Merging #1108 (b5f6a8d) into master (ea9c0a7) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #1108   +/-   ##
=======================================
  Coverage   66.83%   66.83%           
=======================================
  Files         130      130           
  Lines        6320     6320           
=======================================
  Hits         4224     4224           
  Misses       2096     2096           

Flag	Coverage Δ
python-integration	53.97% <ø> (ø)
python-unit	47.86% <ø> (ø)

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