Migrate to Typescript

[farooqkz]

This will help a lot in reducing bugs. I will do it myself as I have to learn.

[Simon-Laux]

some points we need to have (feel free to edit to add more todo points):

Basics

• files with TS need to be called .tsx if they contain jsx tags (html tags in js)
• tsconfig should have the following compiler options:

// if you have an any type you need to write it out
"noImplicitAny": true,
 // makes us handle null and undefined cases, without it ts will only be half as useful
"strictNullChecks": true,
"strict": true

for more compiler options see https://www.typescriptlang.org/tsconfig#compilerOptions

Testing

• add yarn script in package json that calls tsc --noEmit (real typescript compiler) to test for type errors, might be that parcel uses some faster way to translate typescript that doesn't do all checks.
• add this to the testing CI

[farooqkz]

Related: https://github.com/jhsware/inferno-parcel-templates

[farooqkz]

Related: infernojs/inferno#1619

[farooqkz]

Part of it has been done. Commits to master.