Updating release notes

ReleaseNotes/1.4.6.html

@@ -1,3 +1,10 @@
-Fixes/Features in 1.4.6:
+Fixes/Features/Changes in 1.4.6:
 
-* 
+* Universal binary for M1 (arm64) and Intel (x86) macs
+* Minimum supported MacOS version set to 10.14
+* Proper dark mode implementation adding MacOS vibrancy effects in background
+* Supports saving two different pretty print themes (normal and dark mode)
+* Remove double encoding of spaces in URL box (Issue #152)
+* Adds environment variable substitution in headers, specified as ${VAR}
+* Gatekeeper compatible signed release binary
+* Minor UI arrangement tweaks