Update eslint to latest version and fix issues reported (#1352)

* Whitespace fixes in gulpfile.js

* Eslint: fix no-extra-semi

* Eslint: fix no-useless-escape

* Eslint: fix no-constant-condition

* Eslint: fix no-extra-boolean-cast

Also consistent with existing style in LibraryManager.tsx

* Eslint: fix no-prototype-builtins

* Eslint: fix prefer-const

* Eslint: fix no-var

* Eslint: fix no-case-declarations

* Remove unused selectedBoard in reducer

Added in commit 8895ade but never used at any time.

* Eslint: fix no-unused-vars

* Eslint: fix no-control-regex

* Eslint: fix react/no-deprecated

https://reactjs.org/docs/react-component.html#unsafe_componentwillmount

* Eslint: fix react/no-direct-mutation-state

* Add eslint configuration

Created with
    npx eslint --init
and added a couple of rule configurations manually.

Synchronize gulp.src between tslint and eslint.

* Update esllint to latest version

* npm install --save-dev @types/glob

* npm install --save-dev @types/uuid

* npm install --save-dev @types/express

* Remove unecessary await

* Update to latest @types/node

Some of the CI builds failed with

.../vscode-arduino/vscode-arduino/node_modules/@types/connect/index.d.ts(20,42): error TS2689: Cannot extend an interface 'http.IncomingMessage'. Did you mean 'implements'?
TypeScript: 1 semantic error

and apparently this is caused by old @types/node version (previously
version 6.14.9 in this project).

DefinitelyTyped/DefinitelyTyped#41828 (comment)
https://stackoverflow.com/a/59988564/23118
DefinitelyTyped/DefinitelyTyped#41092

Author: hlovdal

.eslintrc.yml

@@ -0,0 +1,24 @@
+env:
+  browser: true
+  es6: true
+extends:
+  - 'eslint:recommended'
+  - 'plugin:react/recommended'
+  - 'plugin:@typescript-eslint/eslint-recommended'
+globals:
+  Atomics: readonly
+  SharedArrayBuffer: readonly
+parser: '@typescript-eslint/parser'
+parserOptions:
+  ecmaFeatures:
+    jsx: true
+  ecmaVersion: 2018
+  sourceType: module
+plugins:
+  - react
+  - '@typescript-eslint'
+rules: {
+  "no-empty": ["error", { "allowEmptyCatch": true }],
+  "no-unused-vars": ["error", { "args": "none" }]
+}
+

gulpfile.js

@@ -1,8 +1,8 @@
 const gulp = require("gulp");
 const eslint = require("gulp-eslint");
 const tslint = require("gulp-tslint");
-const PluginError = require("plugin-error");
-const log = require("fancy-log");
+const PluginError = require("plugin-error");
+const log = require("fancy-log");
 const ts = require("gulp-typescript");
 const sourcemaps = require("gulp-sourcemaps");
 const webpack = require("webpack");
@@ -21,7 +21,7 @@ gulp.task("tslint", () => {
 });
 
 gulp.task("eslint", () => {
-    return gulp.src(["!**/node_modules/**"])
+    return gulp.src(["**/*.ts", "**/*.tsx", "!**/*.d.ts", "!./vendor/**", "!node_modules/**", "!./src/views/node_modules/**", "!out/**"])
         .pipe(eslint())
         .pipe(eslint.format())
         .pipe(eslint.failAfterError());