⚡ Replace “observable” term with “signal” (#19)

* ⚡ refact docs

to make editing (now renaming observables to signal) easier

* ⚡ ⚡ use signal(s) term isntead of observable(s)

* ⚡ 🔤 version + typo

* 🐛 customElement example (0→S)

* 📺 version in package-lock.json

index-with-signals.d.ts

@@ -0,0 +1,2 @@
+export * from "./index";
+export * from "./signals";