Added Remember Me Feature

[tektaxi]

Added Remember Me Feature using localstorage
Closes #112

[psvenk]

@tektaxi Thank you for your contribution. I made a few changes:

• Deleted "my first commit" (using a rebase; if you are interested, you
  can learn more about this technique at https://git-rebase.io/)
  because it is not necessary to include this in the commit log.

• Normalized spacing and indentation: you should take a look at commit
  c8040c2 to see what spacing changes I made (you can also take a look
  at other code in the Aspine codebase, namely scrape.js, serve.js,
  and public/js/home.js, to see what the code style is like). As for
  indentation, you should install the EditorConfig plugin (or enable
  the EditorConfig functionality) for your text editor; if your text
  editor does not have such functionality, I would suggest using one of
  the editors listed on that webpage. My recommendations are Visual Studio
  Code, Emacs, and Vim (and my personal favorite of the three is Vim),
  though Notepad++ has served me well on Windows.

• Made a few other code style changes: I changed let to const in
  some places; the difference between the two is that let allows a
  variable to be reassigned while const does not. It is generally seen
  as good style to use const whenever you do not need to reassign a
  variable. In addition, I changed one instance of == to === and
  renamed a few IDs and variable names to be more semantically accurate. I
  also added semicolons to every statement in your code to be consistent
  with the rest of the codebase (and because JavaScript's automatic
  semicolon insertion sometimes works counterintuitively).

• Moved rememberMe and autofill functions from app.js to a new
  file, login.js, and used event listeners instead of onload and
  onclick. The file app.js is indeed the only JavaScript file used on
  the login page, but it is meant for setting up service workers for
  offline use (this functionality currently is not working) and is also
  called from the main Aspine page. So, I created a new file login.js
  with the login-page–specific code. This allowed me to use event
  listeners instead of making use of onload and onclick, which puts
  all of the logic together in the JavaScript file with just the markup in
  the HTML file.

• Changed the <span> holding the text "Remember me?" to a <label> so
  that the user can click on the text to toggle the checkbox.

Otherwise, this looks good to me. I'll merge this (squashed into one
commit) once someone else takes a look.

[tektaxi]

@psvenk Okay great. Thanks for the help! I'll get better at the syntax like let and const, semicolons, etc. Just not super used to it at the moment.

[kdk1616]

Looks good to me!