Replace use of any in value checker with generic type

CONTRIBUTING.md

@@ -9,7 +9,7 @@ Before anything else, thank you. Thank you for taking some of your precious time
 
 ## Tests
 
-See the `package.json` scripts section for how to run each category of tests.
+Now type `yarn run` or see the `package.json` scripts section for how to run each category of tests.
 
 * lint - `yarn lint`
   * [prettier](https://github.com/prettier/prettier)

src/value_checker.ts

@@ -1,8 +1,8 @@
-export function doesHaveValue(value: any): boolean {
+export function doesHaveValue<T>(value: T): boolean {
   return !doesNotHaveValue(value)
 }
 
-export function doesNotHaveValue(value: any): boolean {
+export function doesNotHaveValue<T>(value: T): boolean {
   return value === null || value === undefined
 }