Added support for multiple profiles in about page (alshedivat#1243)

Addresses alshedivat#963.

Supports two setups: getting profile text from page content.

```markdown
---
layout: about
title: about
permalink: /
subtitle: <a href='#'>Affiliations</a>. Address. Contacts. Moto. Etc.

profiles:
  # if you want to include more than one profile, just replicate the following block
  # and create one content file for each profile inside _pages/
  - align: right
    image: prof_pic.jpg
    # content: about_einstein.md
    image_circular: false # crops the image to make it circular
    more_info: >
      <p>555 your office number</p>
      <p>123 your address street</p>
      <p>Your City, State 12345</p>

news: true  # includes a list of news items
selected_papers: true # includes a list of papers marked as "selected={true}"
social: true  # includes social icons at the bottom of the page
---

Write your biography here. Tell the world about yourself. Link to your favorite [subreddit](http://reddit.com). You can put a picture in, too. The code is already in, just name your picture `prof_pic.jpg` and put it in the `img/` folder.

Put your address / P.O. box / other info right below your picture. You can also disable any these elements by editing `profile` property of the YAML header of your `_pages/about.md`. Edit `_bibliography/papers.bib` and Jekyll will render your [publications page](/al-folio/publications/) automatically.

Link to your social media connections, too. This theme is set up to use [Font Awesome icons](http://fortawesome.github.io/Font-Awesome/) and [Academicons](https://jpswalsh.github.io/academicons/), like the ones below. Add your Facebook, Twitter, LinkedIn, Google Scholar, or just disable all of them.
```

Or getting profile text from `content` (useful when having multiple
profiles).

```markdown
---
layout: about
title: about
permalink: /
subtitle: <a href='#'>Affiliations</a>. Address. Contacts. Moto. Etc.

profiles:
  # if you want to include more than one profile, just replicate the following block
  # and create one content file for each profile inside _pages/
  - align: right
    image: prof_pic.jpg
    content: about_einstein.md
    image_circular: false # crops the image to make it circular
    more_info: >
      <p>555 your office number</p>
      <p>123 your address street</p>
      <p>Your City, State 12345</p>
  - align: left
    image: prof_pic.jpg
    content: about_einstein.md
    image_circular: false # crops the image to make it circular
    more_info: >
      <p>555 your office number</p>
      <p>123 your address street</p>
      <p>Your City, State 12345</p>

news: true  # includes a list of news items
selected_papers: true # includes a list of papers marked as "selected={true}"
social: true  # includes social icons at the bottom of the page
---
```

Which looks like this:


![image](https://user-images.githubusercontent.com/31376482/223251956-aec09f92-55c4-4a17-8ab6-0b30da0970cc.png)

---------

Signed-off-by: George Araújo <george.gcac@gmail.com>
Signed-off-by: George Araujo <george.gcac@gmail.com>