Wpm calculation

[MercMayhem]

• Created new function get_string_till_space to get ExpectedInput string snippet till the space present at or after 'len' argument inputted
• created a function to compare input and expected input snippet and return number correctly typed words
• added tests for both
• changed implementation of the wpm calculation to calculate based on number of correct words typed

Closes #5

[MercMayhem]

@radlinskii can you review this?

[radlinskii]

Hey, Thank you for your contribution, I'm sorry @MercMayhem but I think I won't merge it, and close the issue. I've added the hacktoberfest-label already.

I started to think that this change is just not needed, and might be confusing.

If we were to add this change then we would need to update the colorising of words to display the whole word to some red color to show that the whole word is invalid and won't be counted.

Plus I think changes you made to computing the WPM, are obsolete, we should still count each word as 5 characters. So it would be more like how many characters were typed in the valid words, divided by 5, and that's how many valid "words" were typed.

[MercMayhem]

No problem @radlinskii :) . Loved working on donkeytype. Will definitely be following this project post Hacktoberfest.