Add instruction to use var for declaring variables

[jinolacson]

javascript-3-this/practice.js

Lines 1 to 2 in d25df65

	//We're in a job interview. Answer the following questions (try to not look at your notes unless you have to).
	// 1) What is the purpose of the 'this keyword'?

Change into:

//Note: use var for declaring variables
//We're in a job interview. Answer the following questions (try to not look at your notes unless you have to).
  // 1) What is the purpose of the 'this keyword'?