Sync sieve docs with problem-specifications (#1640)

The sieve exercise has been overhauled as part of a project
to make practice exercises more consistent and friendly.

For more context, please see the discussion in the forum, as well as
the pull request that updated the exercise in the problem-specifications
repository:

- https://forum.exercism.org/t/new-project-making-practice-exercises-more-consistent-and-human-across-exercism/3943
- exercism/problem-specifications#2216

Author: kytrinyx

exercises/practice/sieve/.docs/instructions.md

@@ -1,30 +1,28 @@
 # Instructions
 
-Use the Sieve of Eratosthenes to find all the primes from 2 up to a given
-number.
+Your task is to create a program that implements the Sieve of Eratosthenes algorithm to find prime numbers.
 
-The Sieve of Eratosthenes is a simple, ancient algorithm for finding all
-prime numbers up to any given limit. It does so by iteratively marking as
-composite (i.e. not prime) the multiples of each prime, starting with the
-multiples of 2. It does not use any division or remainder operation.
+A prime number is a number that is only divisible by 1 and itself.
+For example, 2, 3, 5, 7, 11, and 13 are prime numbers.
 
-Create your range, starting at two and continuing up to and including the given limit. (i.e. [2, limit])
+The Sieve of Eratosthenes is an ancient algorithm that works by taking a list of numbers and crossing out all the numbers that aren't prime.
 
-The algorithm consists of repeating the following over and over:
+A number that is **not** prime is called a "composite number".
 
-- take the next available unmarked number in your list (it is prime)
-- mark all the multiples of that number (they are not prime)
+To use the Sieve of Eratosthenes, you first create a list of all the numbers between 2 and your given number.
+Then you repeat the following steps:
 
-Repeat until you have processed each number in your range.
+1. Find the next unmarked number in your list. This is a prime number.
+2. Mark all the multiples of that prime number as composite (not prime).
 
-When the algorithm terminates, all the numbers in the list that have not
-been marked are prime.
+You keep repeating these steps until you've gone through every number in your list.
+At the end, all the unmarked numbers are prime.
 
-The wikipedia article has a useful graphic that explains the algorithm:
-https://en.wikipedia.org/wiki/Sieve_of_Eratosthenes
+```exercism/note
+[Wikipedia's Sieve of Eratosthenes article][eratosthenes] has a useful graphic that explains the algorithm.
 
-Notice that this is a very specific algorithm, and the tests don't check
-that you've implemented the algorithm, only that you've come up with the
-correct list of primes. A good first test is to check that you do not use
-division or remainder operations (div, /, mod or % depending on the
-language).
+The tests don't check that you've implemented the algorithm, only that you've come up with the correct list of primes.
+A good first test is to check that you do not use division or remainder operations.
+
+[eratosthenes]: https://en.wikipedia.org/wiki/Sieve_of_Eratosthenes
+```

exercises/practice/sieve/.docs/introduction.md

@@ -0,0 +1,7 @@
+# Introduction
+
+You bought a big box of random computer parts at a garage sale.
+You've started putting the parts together to build custom computers.
+
+You want to test the performance of different combinations of parts, and decide to create your own benchmarking program to see how your computers compare.
+You choose the famous "Sieve of Eratosthenes" algorithm, an ancient algorithm, but one that should push your computers to the limits.