Favicon for easier browser tab identification

**IMPORTANT: please make sure you ask yourself all intro questions and fill all sections of the template.**

**Before we start...:**

- [X] I checked the documentation and didn't find this feature
- [X] I checked to make sure that this feature has not already been requested

**Branch/Commit:**

Inform what branch/commit/version of "Points" you are using.

`main` branch

**Describe the feature:**

Please include a detailed description of the feature you are requesting and any detail on it’s expected behavior.

> **As a user of Points**
> **I use Points in a browser tab with many other opened tabs**
> **And when I switch tabs and want to go back to Points**
> **And I want to quickly identify which browser tab is the Points one**

**Problem:**

Please include a detailed description of the problem this feature would solve.

> **As a user of Points**
> **I want to see a favicon on the browser tab**
> **So that I can quickly go back to the Points browser tab**

**Mockups:**

N/A - A Points app logo could act as a favicon

**Resources:**

N/A

**I will abide by the [code of conduct](https://github.com/fastruby/points/blob/main/CODE_OF_CONDUCT.md)**