Emit warnings when using svelte/register

[PKlknr]

Is your feature request related to a problem? Please describe.
No warnings are emitted when using svelte/register. I think this line silently ignores them:

svelte/register.js

Line 39 in 3cbe38c

const { js } = compile(fs.readFileSync(filename, 'utf-8'), options);

Describe the solution you'd like
Should svelte/register log warnings when in dev-mode? I guess it could expose them some other way, but I can't see a non-messy one.

Describe alternatives you've considered
I could just re-implement svelte/register.

How important is this feature to you?
I love warnings!

[Conduitry]

Yep, the compile() function used to console.warn the errors itself. During the Svelte v3 changes, we made it return them instead, but we didn't update svelte/register. Logging them in dev mode makes sense to me. I think Svelte v2's svelte/register by default would always display the warnings, dev mode or not. I'm not sure which I prefer.

[Conduitry]

These warnings are now getting displayed by svelte/register in 3.19.0. Thanks!