docs: add project dependencies

Author: MightyCreak

CHANGELOG.md

@@ -23,6 +23,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Linters can be run sooner (before installation)
 - Better messages when an error occurs while parsing the config file
 - Start converting the code to static types
+- Add more information about the dependencies in the documentation
 
 ### Fixed
 - Removed the lasting lint errors (i.e. in main.py)

docs/developers.md

@@ -2,6 +2,40 @@
 
 ## Requirements
 
+Diffuse depends on these projects:
+* Python 3.8+
+* PyPi
+* Cairo and GObject Introspection development headers
+* Meson
+* Flatpak and Flatpak builder
+
+### Install the distribution dependencies
+
+It's a bit difficult to get the command lines for all the distributions and
+their releases, but it should be enough to find the packages on other
+distributions.
+
+<details>
+    <summary>Debian/Ubuntu</summary>
+
+```sh
+sudo apt install python3-pip libcairo2-dev libgirepository1.0-dev meson flatpak flatpak-builder
+```
+
+_Note: Tested on Debian 11 (Buster) and Ubuntu 20.04 (Focal)_
+</details>
+<details>
+    <summary>Fedora</summary>
+
+```sh
+sudo dnf install python-pip python3-cairo-devel python3-gobject-devel meson flatpak flatpak-builder
+```
+
+_Note: Tested on Fedora 34_
+</details>
+
+### Install the project dependencies
+
 To install the requirements just to execute the binary, run:
 
 ```sh