More flexible OS file detection

src/data/config.txt

@@ -126,6 +126,13 @@
 # Default is 0 (disabled).
 #--public-ip-timeout 0
 
+# OS file option
+# Sets the path to the file containing the operating system information.
+# Should be a valid path to an existing file.
+# Note that you might need to run fastfetch with --recache once for it to take affect.
+# Default is /etc/os-release.
+--os-file /etc/os-release
+
 # Key options:
 # Sets the displayed key of a module
 # Can be any string. Some of theme take an argument like a format string. See "fastfetch --help format" for help.

src/data/help.txt

@@ -106,6 +106,7 @@ Library options: Set the path of a library to load
 
 Module specific options:
     --separator-string <str>:     Set the string printed by the separator module
+    --os-file <path>:             Set the path to the file containing OS informations
     --disk-folders <folders>:     A colon separated list of folder paths for the disk output. Default is "/:/home"
     --battery-dir <folder>:       The directory where the battery folders are. Standard: /sys/class/power_supply/
     --localip-show-ipv4 <?value>: Show ipv4 addresses in local ip module. Default is true