chore(templates/deno): add missing typings to devDependencies

[machour]

No description provided.

[MichaelDeBoey]

According to @pcattori, this isn't necessary (see #3117 (comment))

We don't need @types/* nor typescript in devDependencies because users will be relying on Deno tools (like the VSCode Deno extension) to provide types. These tools will use import maps to find the appropriate types (e.g. templates/deno/.vscode/resolve_npm_imports.json).

In short, Deno does typechecking via a custom TS compiler implementation (not via tsc). That implementation doesn't grab types from node_modules/ at all.

[machour]

I am using WebStorm instead of VS Code, and it was complaining to me about this.
Turns out I needed to install the Deno plugin, sorry for the noise!

[MichaelDeBoey]

@machour Had the same problem before indeed