replace base64_cipher.py with an easy to understand version

[hfz1337]

Describe your change:

This PR changes the existing base64_cipher.py with an easy to understand script that explains how the Base64 algorithm works under the hood. The solution is not necessarily faster, but I believe it will help people understand how the algorithm works and why it is possible to use Base64 in Steganography to conceal the existence of a piece of data.
Further more, I believe the base64_cipher.py name can be misleading as Base64 is considered an encoding, and not a cipher.

• Add an algorithm?
• Improve an existing solution.
• 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}.

[github-actions]

This pull request has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.

[stale]

Please reopen this pull request once you commit the changes requested or make improvements on the code. If this is not the case and you need some help, feel free to seek help from our Gitter or ping one of the reviewers. Thank you for your contributions!

[hfz1337]

Thanks for your suggestions.
I made the necessary changes, however, I can't seem to reopen this pull request.
Should I make a new one?

[cclauss]

It is now reopened but conflicts need to be resolved.

[dhruvmanila]

It seems that the bot scanned the file which was deleted and added the require: labels for that. I will make the changes for that.

[hfz1337]

My bad, sorry. Should've used git mv and worked on the old implementation instead of adding a new file and causing all these troubles.

[dhruvmanila]

You can still do that now :)

[hfz1337]

I'll open a new one, I think it will be easier.

[dhruvmanila]

Do not get demotivated by a challenge. Try to overcome the obstacle. Only then you will be able to learn :)

[hfz1337]

Thanks a lot for the advice and motivation.
I opened a new PR here.
Also, I noticed something about algortihms-keeper, when I used an uppercase X to mark respected points in the PR description, it instantly closed the PR. Shouldn't it accept both uppercase and lowercase X as both [x] and [X] are valid in markdown?
It was a bit confusing :p

[dhruvmanila]

Oh, yes completely missed that. Thank you for pointing this out. Also, in the future, if you think the bot is doing something wrong, please open an issue here 😄

P.S. If you want you can open this issue as well :)

[hfz1337]

Sounds cool, thanks! :d