feat(core): update rules [email protected] (#47)

Author: fulls1z3

README.md

@@ -30,8 +30,8 @@ If you have questions, comments or suggestions, just create an issue on this rep
 these rules with new insights, experiences and remarks in alignment with the updates on [TSLint] and [codelyzer].
 
 **Note**: The following set of rules depend on:
-- [TSLint] v5.12.0
-- [codelyzer] ^5.0.0
+- [TSLint] v5.15.0
+- [codelyzer] v5.0.0
 
 ## Table of contents:
 - [Getting started](#getting-started)
@@ -444,6 +444,11 @@ them is allowed by TypeScript*).
 "no-null-keyword": true
 ```
 
+- *Do not use* explicitly declared or implicitly returned **union types** with both **`null`** and **`undefined`** as members.
+```json
+"no-null-undefined-union": true
+```
+
 - *Do not use* **non-null** assertions.
 ```json
 "no-non-null-assertion": true

tslint.json

@@ -112,6 +112,7 @@
     "no-unnecessary-type-assertion": true,
     "callable-types": true,
     "no-null-keyword": true,
+    "no-null-undefined-union": true,
     "no-non-null-assertion": true,
     "array-type": [
       true,