Make TypeScript a peerDependency

[j-f1]

This will make sure users have it installed, preventing an error.

Fixes #264.

[ficristo]

Does the tilde there really works? Just curious.
I found some problems in the past and now I'm using npm i --save-dev --save-prefix=~ typescript@3.1.1

[bradzacher]

it should work fine.
that's the recommended way to signal the version selection prefix.

--save-prefix exists to make it easier to programmatically manipulate the CLI I believe.

[j-f1]

I’m wondering: should the peer dependency be in typescript-estree instead since that’s the package that actually needs it?

[armano2]

@j-f1 we are far behind right typescript-estree right now and this change is not going to be available soon

we will need release of typescript-estree -> typescript-eslint-parser -> eslint-plugin-typescript

[bradzacher]

The problem with leaving it up to typescript-estree is that it's a dependency of a dependency.

So when it shows up in the console people won't easily understand what it is and if they should ignore it.

If we have it as a direct peer dep we can better signal the versions we've tested with as well.

[armano2]

typescript-estree is on typescript@3.2.1 anyway right now, and we are 2 major versions behind.

• Breaking: Bump to typescript-estree@6.0.0, typescript@~3.2.1 eslint/typescript-eslint-parser#576
• Breaking: typescript-estree to 7.0.0 and typescript to 3.2.1 eslint/typescript-eslint-parser#584