Updated C++ requirements, fixes #489

INSTALL.md

@@ -33,15 +33,15 @@ Please refer to [Deployment](#deployment) for further configuration options.
 __Note__: this installation process and the default values of the configuration files have been written for _Debian Bookworm_. Therefore, you may have to adapt commands and/or paths in order to fit to your distribution.
 ### Build dependencies
 __Notes__:
-* a C++17 compiler is needed
+* a C++20 compiler is needed
 * ffmpeg version 4 minimum is required
 ```sh
 apt-get install g++ cmake libboost-program-options-dev libboost-system-dev libavutil-dev libavformat-dev libstb-dev libconfig++-dev ffmpeg libtag1-dev libpam0g-dev libgtest-dev libarchive-dev
 ```
 __Notes__:
 * libpam0g-dev is optional (only for using PAM authentication)
 * libstb-dev can be replaced by libgraphicsmagick++1-dev (the latter will likely use more RAM)
-You also need _Wt4_, which is not packaged yet on _Debian_. See [installation instructions](https://www.webtoolkit.eu/wt/doc/reference/html/InstallationUnix.html).</br>
+You also need _Wt4_, which is not packaged on _Debian_. See [installation instructions](https://www.webtoolkit.eu/wt/doc/reference/html/InstallationUnix.html).</br>
 No optional requirement is needed, except openSSL if you plan not to deploy behind a reverse proxy (which is not recommended).
 ### Build
 Get the latest stable release and build it: