Add simple neural network

[CaioCordeiro]

Describe your change:

• Add an algorithm?
• Fix a bug or typo in an existing algorithm?
• Documentation change?

Checklist:

• I have read CONTRIBUTING.md.
• This pull request is all my own work -- I have not plagiarized.
• I know that pull requests will not be merged if they fail the automated tests.
• This PR only changes one algorithm file. To ease review, please open separate PRs for separate algorithms.
• All new Python files are placed inside an existing directory.
• All filenames are in all lowercase characters with no spaces or dashes.
• All functions and variable names follow Python naming conventions.
• All function parameters and return values are annotated with Python type hints.
• All functions have doctests that pass the automated testing.
• All new algorithms have a URL in its comments that points to Wikipedia or other similar explanation.
• If this pull request resolves one or more open issues then the commit message contains Fixes: #{$ISSUE_NO}.

Tests Results:

Trying:
    res = forward_propagation(32, 10000000)
Expecting nothing
ok
Trying:
    res > 31 and res < 33
Expecting:
    True
ok
Trying:
    res = forward_propagation(32, 1000)
Expecting nothing
ok
Trying:
    res > 31 and res < 33
Expecting:
    False
ok
Trying:
    sigmoid_function(3.5)
Expecting:
    0.9706877692486436
ok
Trying:
    sigmoid_function(3.5, True)
Expecting:
    -8.75
ok
1 items had no tests:
    simple_neural_network
2 items passed all tests:
   4 tests in simple_neural_network.forward_propagation
   2 tests in simple_neural_network.sigmoid_function
6 tests in 3 items.
6 passed and 0 failed.
Test passed.

[CaioCordeiro]

@CaedenPH Could you check this one? The other one got closed when I was fixing the pre-commit.

[CaedenPH]

Looks good.
As a side note, you could also implement a simple doctest check

[CaioCordeiro]

Looks good. As a side note, you could also implement a simple doctest check

Sure, could you show me an example?

[CaedenPH]

Looks good. As a side note, you could also implement a simple doctest check

Sure, could you show me an example?

Very simple, just ```py
if name == "main":
import doctest

doctest.testmod()

@CaioCordeiro 

[CaedenPH]

Suggested change

import doctest

[CaioCordeiro]

Done

[CaedenPH]

Suggested change

	print(doctest.testmod())
	import doctest
	doctest.testmod()

[CaioCordeiro]

Done

[CaedenPH]

Suggested change

	expected = int(input("Expected value: "))
	expected = int(input("Expected value: "))