And add rule "no-var" to eslintrc

Use eslint rule to check the diff between var and let:
    "no-use-before-define": "off"
    "@typescript-eslint/no-use-before-define": 2
    no-redeclare: 2
    block-scoped-var: 2
    no-loop-func: 2
(2) By the way add some eslint rule and unify some code style.

Note: lots of the common type are put in `src/util/types.ts`.

The original logical will never get font configs from the `textStyle` option, and also the `ecModel` doesn't have other font configs except the `textStyle` option.
`var gTextStyleModel = ecModel || ecModel.getModel('textStyle');`