Add setRootView implementation

[Kyle-Ye]

Close #81

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 0% with 61 lines in your changes are missing coverage. Please review.

Project coverage is 14.89%. Comparing base (4318efe) to head (437bf77).
Report is 1 commits behind head on main.

❗ Current head 437bf77 differs from pull request most recent head eb51cb5. Consider uploading reports for the commit eb51cb5 to get more accurate results

Files	Patch %	Lines
...urces/OpenSwiftUI/Core/View/ViewRendererHost.swift	0.00%	37 Missing ⚠️
Sources/OpenSwiftUI/Core/Update/Update.swift	0.00%	14 Missing ⚠️
Sources/OpenSwiftUI/Core/View/ViewGraph.swift	0.00%	6 Missing ⚠️
...rces/OpenSwiftUI/Core/View/ViewGraphDelegate.swift	0.00%	4 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #84      +/-   ##
==========================================
- Coverage   14.98%   14.89%   -0.10%     
==========================================
  Files         188      189       +1     
  Lines        4604     4633      +29     
==========================================
  Hits          690      690              
- Misses       3914     3943      +29     

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