clarify the use of 'unsafe-eval' and what the impact removing it has - Firefox users may not care and disable it to improve security

cfg/conf.sample.php

@@ -68,8 +68,17 @@ languageselection = false
 ; custom scripts from third-party domains to your templates, e.g. tracking
 ; scripts or run your site behind certain DDoS-protection services.
 ; Check the documentation at https://content-security-policy.com/
-; Note: If you use a bootstrap theme, you can remove the allow-popups from the sandbox restrictions.
-; By default this disallows to load images from third-party servers, e.g. when they are embedded in pastes. If you wish to allow that, you can adjust the policy here. See https://github.com/PrivateBin/PrivateBin/wiki/FAQ#why-does-not-it-load-embedded-images for details.
+; Notes:
+; - If you use a bootstrap theme, you can remove the allow-popups from the
+;   sandbox restrictions.
+; - By default this disallows to load images from third-party servers, e.g. when
+;   they are embedded in pastes. If you wish to allow that, you can adjust the
+;   policy here. See https://github.com/PrivateBin/PrivateBin/wiki/FAQ#why-does-not-it-load-embedded-images
+;   for details.
+; - The 'unsafe-eval' is used in two cases; to check if the browser supports
+;   async functions and display an error if not and for Chrome to enable
+;   webassembly support (used for zlib compression). You can remove it if Chrome
+;   doesn't need to be supported and old browsers don't need to be warned.
 ; cspheader = "default-src 'none'; manifest-src 'self'; connect-src * blob:; script-src 'self' 'unsafe-eval'; style-src 'self'; font-src 'self'; img-src 'self' data: blob:; media-src blob:; object-src blob:; sandbox allow-same-origin allow-scripts allow-forms allow-popups allow-modals"
 
 ; stay compatible with PrivateBin Alpha 0.19, less secure