Bump supported browsers for v5

- Chrome history: https://en.wikipedia.org/wiki/Google_Chrome_version_history
- Firefox latest ESR (v60): https://www.mozilla.org/en-US/firefox/organizations/
- Edge history: https://en.wikipedia.org/wiki/Microsoft_Edge#Release_history
- Desktop Safari history: https://en.wikipedia.org/wiki/Safari_version_history
- Opera history: https://help.opera.com/en/opera-version-history/

.browserslistrc

@@ -3,10 +3,10 @@
 >= 1%
 last 1 major version
 not dead
-Chrome >= 45
-Firefox >= 38
-Edge >= 12
-iOS >= 9
-Safari >= 9
-Android >= 4.4
-Opera >= 30
+Chrome >= 70
+Firefox >= 60
+Edge >= 15.15063
+iOS >= 10
+Safari >= 10
+Android >= 5
+Opera >= 50