Observer typo (#101)

* Fixed a typo in the ObserverConstructor new signature

* Polish the ObserverConstructor new signature

* Core version bump

Author: alexanderharding

core/deno.json

@@ -1,6 +1,6 @@
 {
   "name": "@observable/core",
-  "version": "0.15.0",
+  "version": "0.16.0",
   "license": "MIT",
   "exports": "./mod.ts",
   "publish": { "exclude": ["*.test.ts"] }

core/observer.ts

@@ -34,8 +34,8 @@ export interface Observer<Value = unknown> {
  */
 export interface ObserverConstructor {
   /**
-   * Creates and return an object that provides a standard way to [consume](https://jsr.io/@observable/core#consumer)
-   * a sequence of values (either finite or infinite).
+   * Creates and returns an object that provides a standard way to [consume](https://jsr.io/@observable/core#consumer)
+   * a sequence of {@linkcode Value|values} (either finite or infinite).
    * ```ts
    * import { Observer } from "@observable/core";
    *