Making markdown styling more consistent, update README.md and LICENSE.md

[grunt22fox]

This PR makes the markdown styling more consistent in line with similar changes made to the Wii guide through hacks-guide/Guide_Wii#183.

More specifically, this PR does the following:

• Updates the copyright date in the license, as well as the guide pages
• Removing unneeded HTML tags and replacing them with Markdown equivalents (with exceptions)
• Adding badges to the README and rewording things, making it more in line with the Wii guide's README (this is a subjective change)
• Various other markdown changes that I may have forgotten
• Defining clean URLs for the guide (URLs will NOT end in .html)
• Page header TOC will now list headers that are not just H2 level headers
• Remove : from the end of several headers
• Reword several headers to be more readable (e.g. adding Section numbering)
• Capitalization and grammar fixes where needed
• Disable header outlining for various pages that utilize tabs
• Restructure header leveling for various pages
• Fixing markdown links that only say "here", making them more descriptive
• Adding formatting to some code blocks that did not have them before
• Reformat tables to be cleaner in the markdown code, but otherwise unchanged (unless refined)
• Delete an unused image in the homebrew directory`

Several page specific changes are also made. These include:

• index.md: Complete overhaul and reorganization of page content

-- extras --

• extras/adding_udev.md: Create shell formatted codeblocks for the listed commands
• extras/blocking_nintendo.md: Move various instructions for 90DNS into a tab format
• extras/glossary.md: Change glossary into a formatted table instead of several bullet points
• extras/installing_android.md: Recreate SD card file structure diagram

-- user_guide --

• user_guide/all/sd_preparation.md: Recreate SD card file structure diagram

I omitted the markdown styling guidelines that I drafted on the Wii guide's README, as this is not a guide that I actively contribute to. I would appreciate feedback in the comments about if this is something that might be desired. I also copied over the markdownlint.json that I used for linting to accomplish some of these changes but it can also be removed if desired.

Resolves #241, as there are no broken links for images or guide pages as far as I could tell.
Resolves #242, as I reworded the applicable instructions in sd_preparation.md to be quite specific about what to do.
Resolves #255, as I added a warning to transfer_sd.md that advises to follow instructions that were already posted in faq.md to resolve the mentioned issue.