This commit adds support for multiple entry points to `deno doc`.
Unfortunately to achieve that, I had to change the semantics of the
command to explicitly require `--filter` parameter for filtering
symbols, instead of treating second free argument as the filter argument.
`deno doc --builtin` is still supported, but cannot be mixed with
actual entrypoints.
Upgrades to deno_doc 0.70 which includes the feature for showing
non-exported types referenced in exported types as well as a much more
advanced deno doc that uses a symbol graph.
