Add Mac OS dependencies notes

CHANGELOG.md

@@ -15,6 +15,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - [Datumaro] CLI command for dataset equality comparison (<https://github.com/opencv/cvat/pull/1989>)
 - [Datumaro] Merging of datasets with different labels (<https://github.com/opencv/cvat/pull/2098>)
 - Add FBRS interactive segmentation serverless function (<https://github.com/openvinotoolkit/cvat/pull/2094>)
+- MacOS users notes in CONTRIBUTING.md
 
 ### Changed
 - UI models (like DEXTR) were redesigned to be more interactive (<https://github.com/opencv/cvat/pull/2054>)

CONTRIBUTING.md

@@ -9,18 +9,24 @@ they should reciprocate that respect in addressing your issue or assessing
 patches and features.
 
 ## Development environment
-
-Next steps should work on clear Ubuntu 18.04.
-
 -   Install necessary dependencies:
+
+    Ubuntu 18.04
     ```sh
     sudo apt-get update && sudo apt-get --no-install-recommends install -y build-essential curl redis-server python3-dev python3-pip python3-venv python3-tk libldap2-dev libsasl2-dev pkg-config libavformat-dev libavcodec-dev libavdevice-dev libavutil-dev libswscale-dev libswresample-dev libavfilter-dev
     ```
-    Please make sure you have installed FFmpeg libraries (libav*) version 4.0 or higher.
     ```sh
     # Node and npm (you can use default versions of these packages from apt (8.*, 3.*), but we would recommend to use newer versions)
     curl -sL https://deb.nodesource.com/setup_12.x | sudo -E bash -
     sudo apt-get install -y nodejs
+    ```
+
+    MacOS 10.15
+    ```sh
+    brew install git python pyenv redis curl openssl node
+    ```
+
+-   Install FFmpeg libraries (libav*) version 4.0 or higher.
 
 -   Install [Visual Studio Code](https://code.visualstudio.com/docs/setup/linux#_debian-and-ubuntu-based-distributions)
 for development
@@ -36,6 +42,11 @@ for development
     python manage.py migrate
     python manage.py collectstatic
     ```
+    > Note for Mac users
+    >
+    > If you have any problems with installing dependencies from
+    > ```cvat/requirements/*.txt```, you may need to reinstall your system python
+    > In some cases after system update it can be configured incorrectly and cannot compile some native modules
 
 -   Create a super user for CVAT:
     ```sh
@@ -52,6 +63,13 @@ for development
     cd cvat-core && npm install && \
     cd ../cvat-ui && npm install && npm start
     ```
+    > Note for Mac users
+    >
+    > If you faced with error
+    >
+    > ```Node Sass does not yet support your current environment: OS X 64-bit with Unsupported runtime (57)```
+    >
+    > Read this article [Node Sass does not yet support your current environment](https://marketplace.visualstudio.com/items?itemName=msjsdiag.debugger-for-chrome)
 
 -   Open new terminal (Ctrl + Shift + T), run Visual Studio Code from the virtual environment
     ```sh