Update changelog for v5.4.0 and the license year to 2020 (#1000)

Co-authored-by: Akash Nimare <akashnimare@users.noreply.github.com>

changelog.md

@@ -2,6 +2,25 @@
 
 All notable changes to the Zulip desktop app are documented in this file.
 
+### v5.4.0 --2020-07-21
+
+**New features**:
+* Added support for certificates from system store.
+* Added support for Slovak as application language.
+
+**Fixes**:
+* Fix bug in *Copy Link* and add *Copy Email* option in context menu.
+* Enable *Copy* option in context menu only when copying is possible.
+* Remove leading and trailing separators in context menu on non-mac systems.
+* ignoreCerts: Accommodate WebSocket URLs in certificate-error handler.
+
+**Dependencies**:
+* Upgrade all dependencies, including Electron 8.4.0.
+
+**Deprecations**:
+* This release supports certificates from Zulip store as well as system store. Zulip certificate store will be deprecated in the next release.
+Users are hereby requested to move to system store. For more information, please see the [documentation](https://zulip.com/help/custom-certificates).
+
 ### v5.3.0 --2020-06-24
 
 **Security fixes**:

package.json

@@ -50,7 +50,7 @@
     "files": [
       "app/**/*"
     ],
-    "copyright": "©2019 Kandra Labs, Inc.",
+    "copyright": "©2020 Kandra Labs, Inc.",
     "mac": {
       "category": "public.app-category.productivity",
       "target": [