fix TSDoc comments (reduxjs#3560)

Former-commit-id: 48de485
Former-commit-id: 150b5f7

src/applyMiddleware.ts.REMOVED.git-id

@@ -1 +1 @@
-7bddf3fc0594f56bdef8979d7114a12f926e7d61
+f73584325282b69e12dd6caa61ae5bf23c32e64f

src/compose.ts.REMOVED.git-id

@@ -1 +1 @@
-2ed13051a2557deb787f9c125d1bbdb208a374fc
+fcbfd70d7bf2aa262de58be558c4a6008957e7f0

src/createStore.ts.REMOVED.git-id

@@ -1 +1 @@
-0a0d35b8351fe8bd318d6c754b31d3ed210698d6
+a75fc2a304526089ddb4af859689430dc4e4b3c6

src/types/middleware.ts.REMOVED.git-id

@@ -0,0 +1 @@
+d631d988daabb5d9d72c5821122fede3a8e705b2

src/utils/isPlainObject.ts

@@ -1,8 +1,8 @@
 /**
- * @param {any} obj The object to inspect.
- * @returns {boolean} True if the argument appears to be a plain object.
+ * @param obj The object to inspect.
+ * @returns True if the argument appears to be a plain object.
  */
-export default function isPlainObject(obj: unknown) {
+export default function isPlainObject(obj: any): boolean {
   if (typeof obj !== 'object' || obj === null) return false
 
   let proto = obj

src/utils/warning.ts

@@ -1,10 +1,9 @@
 /**
  * Prints a warning in the console if it exists.
  *
- * @param {String} message The warning message.
- * @returns {void}
+ * @param message The warning message.
  */
-export default function warning(message: string) {
+export default function warning(message: string): void {
   /* eslint-disable no-console */
   if (typeof console !== 'undefined' && typeof console.error === 'function') {
     console.error(message)