chore: update ts target to es2020

Targeting ES2020 looks like it's generally fine today. It's widely supported across modern browsers
and environments and it would allow Semaphore bundles to use new ES features natively, like arrow
functions, promises, and classes, which can improve code readability and efficiency.

re #232

tsconfig.json

@@ -2,7 +2,7 @@
     "compilerOptions": {
         "baseUrl": ".",
         "strict": true,
-        "target": "ES6",
+        "target": "ES2020",
         "module": "ESNext",
         "moduleResolution": "Bundler",
         "esModuleInterop": true,