Prepare monorepo for typescript migration

[svallory]

We'll migrate the entire source code to Typescript. This issue tracks the whole migration progress while each package migration will be done in its own issue.

In this task, we will set up a base tsconfig.json, eslint, editorconfig, and Prettier so we follow the same development pattern and style in all packages.

All configuration should be based on @tokilabs/config packages

• Setup tsconfig.json #16
• Setup ESLint
• Create .editorconfig
• Setup Prettier

But the full migration will only be completed when all the issues below are done and merged to this issues branch.

• Migrate pug-attrs package to Typescript #2
• Migrate pug-cli package to Typescript #3
• Migrate pug-code-gen to Typescript #4
• Migrate pug-error to Typescript #5
• Migrate pug-filters to Typescript #6
• Migrate pug-lexer to Typescript #7
• Migrate pug-linker to Typescript #8
• Migrate pug-load to Typescript #9
• Migrate pug-parser to Typescript #10
• Migrate pug-runtime to Typescript #11
• Migrate pug-strip-comments to Typescript #12
• Migrate pug-walk to Typescript #13
• Migrate pug to Typescript #14