Update legibility of formula to proper Latex Format

[CloudChaoszero]

Description

• Update Normal Distribution's PDF formula in the Developer Guide section to proper latex format
• Add wiki hyperlink to PDF definition

Note: Added mid-step just to clarify why the PDF is resulted, as such.

Closes #4384

Output

From

cd docs/source
make html
make serve

We get

[codecov]

Codecov Report

Merging #4390 (1426c46) into master (3cfee77) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #4390   +/-   ##
=======================================
  Coverage   88.04%   88.04%           
=======================================
  Files          88       88           
  Lines       14482    14482           
=======================================
  Hits        12750    12750           
  Misses       1732     1732           

[MarcoGorelli]

Thanks @CloudChaoszero

Instead of writing where\mu=0, would it work to use the vertical "evaluated at" line (https://tex.stackexchange.com/questions/40160/math-symbol-question-vertical-bar-for-evaluated-at)?

Finally, I think the * sign, and the brackets around 2*\pi could be removed

[CloudChaoszero]

@MarcoGorelli Sounds great. Made the update, seen below

[MarcoGorelli]

Thanks, looks good, but I think you'll want the vertical "evaluated at" line after the third operand, not after the fourth one

Also, could you address

I think the * sign, and the brackets around 2*\pi could be removed

Finally, there's a linting error due to trailing whitespace, could you resolve that please? See the style guide for how to run the checks, and feel free to ask if it's unclear

[CloudChaoszero]

@MarcoGorelli , Ah, thanks for the tip--found and deleted the whitespace.

Moreover, I resolved the following & 'evaluated at' piece.

I think the * sign, and the brackets around 2*\pi could be removed

[twiecki]

Thanks @CloudChaoszero!