Rename @stlite/mountable to @stlite/web (or some more general name)

[whitphx]

When I named the module as mountable, I intended to avoid occupying the too general name space,
but it has been revealed that there are no other sub packages suitable for the web name and there shouldn't be any confusion.

@stlite/web has a contrast to @stlite/desktop.

[whitphx]

https://chatgpt.com/share/673de8cf-9640-800a-b48a-dd5e2ab1e938

• @stlite/webapp
• @stlite/browser
• @stlite/embed
• @stlite/html
• @stlite/spa
• @stlite/page
• @stlite/site
• @stlite/portal

[whitphx]

Will use @stlite/browser.
It looks good in a form of import { mount } from "@stlite/browser".

@stlite/web is too vague.
@stlite/webapp sounds like it's a prebuilt web app.
@stlite/embed: "embed" is slightly different from what it actually does.