Rewrite alignment newsletter module

[Lovkush-A]

initially intention was to only introduce typehints, but I ended up making many changes so better to have separate PR.

note that there should be no changes to functionality with this pr

Changes include:

• adding docstrings and typehints and comments
• adding global constants for numerical constants
• renaming variables / methods
• simplifying (in my view) the sequence of method calls. instead of method1 calling method2 calling method3 calling method4, now have method1 which calls method2, method 3 and method 4 in a sequence.
• adding two test cases
• moving Item class outside of main class.
• reducing indentation levels for easier readability (in my opinion)

[Lovkush-A]

there is unusual bug with s, test yourself, where the test response is somehow lost.

TEST_RESPONSE 25: This seems relevant:
Adversarial Examples Are Not Bugs, They Are Features
...
TEST_RESPONSE 26: No matches found in the Alignment Newsletter Database
...
QUESTION # 25: FAILED
The sent message was 'TEST_QUESTION 25: paper search bugs features'
the expected message was 'REGULAR EXPRESSION: This seems relevant:\n.?Adversarial Examples Are Not Bugs, They Are Features'
the received message was 'NEVER RECEIVED A RESPONSE'
QUESTION # 26: FAILED
The sent message was 'TEST_QUESTION 26: blog post search: thisisnotarealword'
the expected message was 'No matches found in the Alignment Newsletter Database'
the received message was 'NEVER RECEIVED A RESPONSE'

[Lovkush-A]

made most of aesthetic suggestions as suggested by @MatthewBaggins. thanks for the review!