Enable typescript strict checks

Author: vishwam

src/fetch.ts

@@ -110,7 +110,7 @@ export function fetchEventSource(input: RequestInfo, {
 
                 await onopen(response);
 
-                await getBytes(response.body, getLines(getMessages(id => {
+                await getBytes(response.body!, getLines(getMessages(id => {
                     if (id) {
                         // store the id and send it back on the next retry:
                         headers[LastEventId] = id;

tsconfig.json

@@ -2,13 +2,15 @@
     "compilerOptions": {
         "target": "ES2017",
         "module": "commonjs",
+        "esModuleInterop": true,
         "forceConsistentCasingInFileNames": true,
         "rootDir": "src",
         "outDir": "lib/cjs",
         "declaration": true,
         "sourceMap": true,
+        "skipLibCheck": true,
+        "strict": true,
         "removeComments": true,
-        "noImplicitAny": false,
         "noFallthroughCasesInSwitch": true,
         "noUnusedLocals": true,
         "noUnusedParameters": true,