docs: add first draft for kusion server design doc

[ffforest]

What type of PR is this?

What this PR does / why we need it:

Which issue(s) this PR fixes:

Fixes #

Special notes for your reviewer:

Does this PR introduce a user-facing change?

Additional documentation e.g., design docs, usage docs, etc.:

[ffforest]

@hoangndst if you are interested

[coveralls]

Pull Request Test Coverage Report for Build 10094360900

Details

• 0 of 0 changed or added relevant lines in 0 files are covered.
• 3 unchanged lines in 1 file lost coverage.
• Overall coverage decreased (-0.02%) to 54.101%

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Files with Coverage Reduction	New Missed Lines	%
pkg/engine/operation/parser/parser.go	3	79.27%
<!--	Total:	3

Totals
Change from base Build 10089957744:	-0.02%
Covered Lines:	9400
Relevant Lines:	17375

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💛 - Coveralls