Should add center time-tag inside every input time-tag in the input list.

[andy840119]

Inspired from #157
Should make something like the image below:

If not add the end time-tag before the next time-tag, will let the lyric effect moving faster because moving position will include that spacing.
This issue might be noticed if the character spacing become larger.

How to implement:

• Make internal static function to calculate the value that need to be insert between every input time-tag.
• Write a test case to check calculating result.

[andy840119]

https://stackoverflow.com/questions/26753272/linq-adding-an-item-to-every-second-position

Not really sure will have better linq function for the case to insert value between every element.
This is the most similar cases i found.

string[] list = { "BCA", "MCA", "MBA", "MA", "CA", "BBA" };
        
List<string> result = list.Aggregate(new List<string>(0), (a, x) => { 
	// a.Clear();
	a.Add("=="); 
	a.Add(x); 
	return a; 
});

Console.WriteLine(result.Count());
foreach(var aaa in result)
{
	Console.WriteLine(aaa);
}

Result:

12
==
BCA
==
MCA
==
MBA
==
MA
==
CA
==
BBA

[andy840119]

http://boson4.phys.tku.edu.tw/numerical_methods/nm_units/interpolation_n_extrapolation_intro_n_polynomial.htm
Hmm...
Seems like it's named Interpolation (差值)
Maybe it should be called something like GetInterpolatedTimeTags and GetInterpolatedTimeTagsBetweenTwoTimeTag(TimeTag first, TimeTag second).

[andy840119]

This pull-request include the case with reverse time-tag.
So guess this issue should be able to close.