Fix subrouter ssr

[pierregradelet]

• Fix no render of children stack in ssr
• Add props "as" on Stack to use div instead of main for subrouter

[willybrauner]

size-limit report 📦

Path	Size
@cher-ami/router	9.82 KB (+11.12% 🔺)

[codesandbox-ci]

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Sandbox	Source
example-client	Configuration
example-ssr	Configuration
example-history-block	Configuration
example-hashhistory	Configuration