Fix style of the first ten solutions for Project Euler (#3242)

* Fix style of the first ten solutions for Project Euler

- Unify the header docstring, and add reference URLs to wikipedia
  or similar
- Fix docstrings to be properly multilined
- Add newlines where appropriate
- Add doctests where they were missing
- Remove doctests that test for the correct solution
- fix obvious spelling or grammar mistakes in comments and
  exception messages
- Fix line endings to be UNIX. This makes two of the files seem
  to have changed completely
- no functional changes in any of the solutions were done
  (except for the spelling fixes mentioned above)

* Fix docstrings and main function as per Style Guide

project_euler/problem_002/sol4.py

@@ -1,21 +1,27 @@
 """
-Problem:
-Each new term in the Fibonacci sequence is generated by adding the previous two
-terms. By starting with 1 and 2, the first 10 terms will be:
+Project Euler Problem 2: https://projecteuler.net/problem=2
 
-    1,2,3,5,8,13,21,34,55,89,..
+Even Fibonacci Numbers
+
+Each new term in the Fibonacci sequence is generated by adding the previous
+two terms. By starting with 1 and 2, the first 10 terms will be:
+
+1, 2, 3, 5, 8, 13, 21, 34, 55, 89, ...
 
 By considering the terms in the Fibonacci sequence whose values do not exceed
-n, find the sum of the even-valued terms. e.g. for n=10, we have {2,8}, sum is
-10.
+four million, find the sum of the even-valued terms.
+
+References:
+    - https://en.wikipedia.org/wiki/Fibonacci_number
 """
 import math
 from decimal import Decimal, getcontext
 
 
 def solution(n: int = 4000000) -> int:
-    """Returns the sum of all fibonacci sequence even elements that are lower
-    or equals to n.
+    """
+    Returns the sum of all even fibonacci sequence elements that are lower
+    or equal to n.
 
     >>> solution(10)
     10
@@ -32,26 +38,27 @@ def solution(n: int = 4000000) -> int:
     >>> solution(0)
     Traceback (most recent call last):
         ...
-    ValueError: Parameter n must be greater or equal to one.
+    ValueError: Parameter n must be greater than or equal to one.
     >>> solution(-17)
     Traceback (most recent call last):
         ...
-    ValueError: Parameter n must be greater or equal to one.
+    ValueError: Parameter n must be greater than or equal to one.
     >>> solution([])
     Traceback (most recent call last):
         ...
-    TypeError: Parameter n must be int or passive of cast to int.
+    TypeError: Parameter n must be int or castable to int.
     >>> solution("asd")
     Traceback (most recent call last):
         ...
-    TypeError: Parameter n must be int or passive of cast to int.
+    TypeError: Parameter n must be int or castable to int.
     """
+
     try:
         n = int(n)
     except (TypeError, ValueError):
-        raise TypeError("Parameter n must be int or passive of cast to int.")
+        raise TypeError("Parameter n must be int or castable to int.")
     if n <= 0:
-        raise ValueError("Parameter n must be greater or equal to one.")
+        raise ValueError("Parameter n must be greater than or equal to one.")
     getcontext().prec = 100
     phi = (Decimal(5) ** Decimal(0.5) + 1) / Decimal(2)
 
@@ -62,4 +69,4 @@ def solution(n: int = 4000000) -> int:
 
 
 if __name__ == "__main__":
-    print(solution(int(input().strip())))
+    print(f"{solution() = }")