Inform users about Pyside6 and conmon packages

Inform users that for specific distros and versions, we install some
extra packages (PySide6, conmon), in order to fix some incompatibilities
between Dangerzone and the base system. Provide also a link to the
source / build instructions for the package, as well as any relevant
issues.

Fixes #767

BUILD.md

@@ -20,6 +20,8 @@ Install dependencies:
   sudo cp ./dev_scripts/apt-tools-prod.pref /etc/apt/preferences.d/
   ```
 
+  The `conmon` package provided in the above repo was built with the
+  following [instructions](https://github.com/freedomofpress/maint-dangerzone-conmon/tree/ubuntu/jammy/fpf).
   Alternatively, you can install a `conmon` version higher than `v2.0.25` from
   any repo you prefer.
 

INSTALL.md

@@ -49,6 +49,18 @@ Dangerzone is available for:
   ```
 </details>
 
+<details>
+  <summary><i>:memo: Notice for `conmon` package on Ubuntu 22.04 (Jammy).</i></summary>
+  </br>
+
+  The `conmon` version that Podman uses and Ubuntu Jammy ships, has a bug
+  that gets triggered by Dangerzone
+  (more details in https://github.com/freedomofpress/dangerzone/issues/685).
+  To fix this, we provide our own `conmon` package through our APT repo, which
+  was built with the following [instructions](https://github.com/freedomofpress/maint-dangerzone-conmon/tree/ubuntu/jammy/fpf).
+
+</details>
+
 Add our repository following these instructions:
 
 Download the GPG key for the repo:
@@ -96,6 +108,17 @@ sudo apt install -y dangerzone
 
 ### Fedora
 
+<details>
+  <summary><i>:memo: Notice for `python3-pyside6` package on Fedora 39/40.</i></summary>
+  </br>
+
+  The Fedora 39/40 repos do not provide official Python bindings for Qt. For
+  this reason, we provide our own `python3-pyside6` package from our YUM repo
+  (see [build instructions](https://github.com/freedomofpress/maint-dangerzone-pyside6)).
+  For a deeper dive on this subject, you may read [this issue](https://github.com/freedomofpress/dangerzone/issues/211#issuecomment-1827777122)
+
+</details>
+
 Type the following commands in a terminal:
 
 ```