~/.Xresources: Fix url selection.

.Xresources

URxvt.perl-ext-common:      default,url-select
URxvt.keysym.M-u:           perl:url-select:select_next
URxvt.urlLauncher:          chromium
URxvt.underlineURLs:        true
URxvt.url-select.launcher:  chromium
URxvt.url-select.underline: true