docs(reject-function-type): add more examples; closes #1568

Co-credit @TheJaredWilcurt

Author: brettz9

docs/rules/reject-function-type.md

@@ -22,15 +22,17 @@ The following patterns are considered problems:
 
 ````ts
 /**
- * @param {Function} abc
+ * @param {Function} fooBar
  */
-function quux () {}
+function quux (fooBar) {
+  console.log(fooBar(3));
+}
 // Message: Prefer a more specific type to `Function`
 
 /**
  * @param {string|Array<Function>} abc
  */
-function quux () {}
+function buzz (abc) {}
 // Message: Prefer a more specific type to `Function`
 ````
 
@@ -46,6 +48,28 @@ The following patterns are not considered problems:
 /**
  * @param {SomeType} abc
  */
-function quux () {}
+function quux (abc) {}
+
+// To avoid referencing a generic Function, define a callback
+//   with its inputs/outputs and a name.
+/**
+ * @callback          FOOBAR
+ * @param    {number} baz
+ * @return   {number}
+ */
+
+
+// Then reference the callback name as the type.
+/**
+ * @param {FOOBAR} fooBar
+ */
+function quux (fooBar) {
+  console.log(fooBar(3));
+}
+
+/**
+ * @param {string|Array<FOOBAR>} abc
+ */
+function buzz (abc) {}
 ````
 

test/rules/assertions/rejectFunctionType.js

@@ -3,9 +3,11 @@ export default {
     {
       code: `
         /**
-         * @param {Function} abc
+         * @param {Function} fooBar
          */
-        function quux () {}
+        function quux (fooBar) {
+          console.log(fooBar(3));
+        }
       `,
       errors: [
         {
@@ -19,7 +21,7 @@ export default {
         /**
          * @param {string|Array<Function>} abc
          */
-        function quux () {}
+        function buzz (abc) {}
       `,
       errors: [
         {
@@ -35,7 +37,32 @@ export default {
         /**
          * @param {SomeType} abc
          */
-        function quux () {}
+        function quux (abc) {}
+      `,
+    },
+    {
+      code: `
+        // To avoid referencing a generic Function, define a callback
+        //   with its inputs/outputs and a name.
+        /**
+         * @callback          FOOBAR
+         * @param    {number} baz
+         * @return   {number}
+         */
+
+
+        // Then reference the callback name as the type.
+        /**
+         * @param {FOOBAR} fooBar
+         */
+        function quux (fooBar) {
+          console.log(fooBar(3));
+        }
+
+        /**
+         * @param {string|Array<FOOBAR>} abc
+         */
+        function buzz (abc) {}
       `,
     },
   ],