📚️ docs: add example usage

Added example usage of the library and made a better TODO list.

README.md

@@ -2,6 +2,20 @@
 A simple JSON Library for java, still in development.
 
 ### TODO:
- - Add JSON variables to file
- - Check each line for searching variables
- - ... many more
+ - Add JSON variables to file;
+ - Read file for existing variables before writing new ones;
+ - Only write when `JSONBuilder.makeJSON()` is called;
+ - Make a JSONFormatter class.
+
+### Usage
+Here's an example usage of JSONutils:
+```java
+JSON jsonFile = new JSONBuilder("/directory/file.json").newVariable("IsLibraryComplete", false).makeJSON();
+```
+**Explanation**:
+ - `jsonFile` is an instance of the JSON class;
+ - `jsonFile` is instantiated using JSONBuilder for adding variables and building the JSON using `makeJSON()`;
+ - `JSONBuilder` has(not yet) many methods to build a JSON file, such as `newVariable(String key, Object value)`, and `makeJSON()`;
+ - `JSONBuilder` is extended from the `JSON` class;
+ - `makeJSON()` has to be used in the end of the line;
+ - `newVariable()` adds the variable to a HashMap, which in `makeJSON()` will be written to a file, just like `Writer.flush()`.