Upgrade typescript

[noelia-lencina]

Notes:

• The new version of @typescript-eslint/eslint-plugin needs node >= 12.0.0.
• Tested this with the repo for which the original problem was reported and it solves it.
• This will require the user to update their rules to adjust to the breaking changes that have been introduced in https://github.com/typescript-eslint/typescript-eslint/blob/master/CHANGELOG.md#200-2019-08-13 (the minimum version for fixing the issue reported by the user is 2.5.0 and after that there are no breaking changes)