Add and configure ESLint and update configuration for Prettier (#391)

* Apply ESLint config and update Prettier

* Update dependencies and rebuild

* Update docs

src/setup-dotnet.ts

@@ -13,7 +13,7 @@ const qualityOptions = [
   'ga'
 ] as const;
 
-export type QualityOptions = typeof qualityOptions[number];
+export type QualityOptions = (typeof qualityOptions)[number];
 
 export async function run() {
   try {
@@ -100,7 +100,7 @@ export async function run() {
 }
 
 function getVersionFromGlobalJson(globalJsonPath: string): string {
-  let version: string = '';
+  let version = '';
   const globalJson = JSON.parse(
     // .trim() is necessary to strip BOM https://github.com/nodejs/node/issues/20649
     fs.readFileSync(globalJsonPath, {encoding: 'utf8'}).trim()