Add dark logos

[BernatBC]

Issue

Closes #902

Description

The config for using this feature looks like this:

- name: Studies
  icon: fa-graduation-cap
  timeframe: August 2023 - December 2023
  institution:
    name: University
    url: "https://www.example.com"
    logo: /images/school.png
    darkLogo: /images/school-dark.png

Basically, we just added:

    darkLogo: /images/school-dark.png

Test Evidence

I've provided two images. logo has black letters, and darkLogo has white letters. You can see below what's the behavior depending on the images provided

I'll add it to the guides after you approve it.

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[hossainemruz]

NICE!