[11.x] Implement formatting of fractions

[shaedrich]

Follow-up to #48845

Features

• proper/improper fractions: When the numerator and the denominator are both positive, the fraction is called proper if the numerator is less than the denominator, and improper otherwise (e.g. 1 3/4 is "proper" while 7/4 is the same decimal in "improper" notation)
• approximation: Not all decimals can be mapped 1:1 to fractions and vice versa. Especially, repeating decimals can sometimes be written as a fraction but not as a decimal without using additional notation (e.g. 1/3 can be approximated to 0.33, but the actual decimal would be 0.33… or 0. ̅3)
• stylization: We, especially when writing digitally, often resort to a simplified notation for fractions (e.g. 3/4). Actually, these would have to be written with unicode characters. This notation has to options: Just marking the numerator and denominator as part of a fraction with a unicode slash and leave the rendering to the output or display the three parts manually as subscript and superscript.
  • What is the correct way to write fractions in Unicode? on superuser.com
  • Unicode subscripts and superscripts on wikipedia.org

Examples (see tests)

Input	Limes	improper	approximation	stylization	glue	Output
0.06	default	default	default	default	default	null
0.75	default	default	default	default	default	3/4
1.75	default	default	default	default	default	1 3/4
1.75	default	true	default	default	default	7/4
2.33	default	default	default	default	default	2 1/3
2.33	default	default	default	default	default	2 1/3
2.33	default	default	false	default	default	null
2.58	default	default	default	default	default	2 4/7
2.58	5	default	default	default	default	2 3/5
1.97	default	default	default	default	default	2
1.75	default	default	default	default	default	1 3/4
1.75	default	default	default	false	default	1 3/4
1.75	default	default	default	auto	default	1 3⁄4
1.75	default	default	default	manual	default	1 ³⁄₄
1.75	default	default	default	manual	''	1³⁄₄

[taylorotwell]

Thanks for your pull request to Laravel!

Unfortunately, I'm going to delay merging this code for now. To preserve our ability to adequately maintain the framework, we need to be very careful regarding the amount of code we include.

If applicable, please consider releasing your code as a package so that the community can still take advantage of your contributions!