Update documentation. (#880)

### Prerequisites

- [x] This pull request fixes a bug.
- [ ] This pull request adds a feature.
- [ ] This pull request introduces breaking change.

### Description

Updates & adds documentation.

### Issues Resolved

No issue created for this missing documentation.

### Checklist

#### General

- [x] Describe what changes are being made
- [x] Explain why and how the changes were necessary and implemented
respectively
- [ ] Reference issue with `#<ISSUE_NO>` if applicable

#### Resources

- [ ] If you have changed any SCSS code, run `make release` to
regenerate all CSS files

#### Contributors

- [x] Add yourself to `CONTRIBUTORS.md` if you aren't on it already

---------

Co-authored-by: Luiz F. A. de Prá <luizdepra@users.noreply.github.com>

CONTRIBUTORS.md

@@ -138,4 +138,5 @@
 - [iron3oxide](https://github.com/iron3oxide)
 - [Jens Rantil](https://github.com/JensRantil)
 - [Muqeet Malik](https://github.com/mmalik23)
+- [Sammy44nts](https://github.com/sammy44nts)
 

docs/configurations.md

@@ -115,7 +115,9 @@ These are all the parameters used by `hugo-coder` theme.
 | faviconSVG                    | string | No       | Custom path to a SCG favicon.                    | `"/img/favicon.svg"`             | `"/img/favicon.svg"`                             |
 | favicon_32                    | string | No       | Custom path to a 32x32 favicon.                  | `"/img/favicon-32x32.png"`       | `"/img/favicon-32x32.png"`                       |
 | favicon_16                    | string | No       | Custom path to a 16x16 favicon.                  | `"/img/favicon-16x16.png"`       | `"/img/favicon-16x16.png"`                       |
-| touchIcon                     | string | No       | Custom path to a touch-icon                      | `"/images/apple-touch-icon.png"` | `"/images/apple-touch-icon.png"`                 |
+| touchIcon                     | string | No       | Custom path to an apple-touch-icon                      | `"/images/apple-touch-icon.png"` | `"/images/apple-touch-icon.png"`                 |
+| mask_icon                     | string | No       | Custom path to a mask-icon                      | `"/images/safari-pinned-tab.svg"` | `"/images/safari-pinned-tab.svg"`                 |
+| mask_icon_color                     | string | No       | Custom color for mask-icon color                      | `"#5bbad5"` | `"#5bbad5"`                 |
 | since                         | string | No       | Date shown in the footer before now year         |                                  | `"2020"`                                         |
 | maxSeeAlsoItems               | number | No       | Series see also post count                       | `5`                              | `10`                                             |
 | commit                        | string | No       | Show the last git commit in the footer           |                                  | `"https://github.com/luizdepra/hugo-coder/tree/"`|