css: Use SCSS nesting in alerts.scss for `.alert`.
css: Use SCSS nesting in alerts.scss for `.alert`.

tommyip/zulip,brainwane/zulip,showell/zulip,eeshangarg/zulip,rht/zulip,kou/zulip,hackerkid/zulip,tommyip/zulip,showell/zulip,brainwane/zulip,synicalsyntax/zulip,timabbott/zulip,zulip/zulip,rishig/zulip,synicalsyntax/zulip,kou/zulip,synicalsyntax/zulip,showell/zulip,punchagan/zulip,tommyip/zulip,brainwane/zulip,showell/zulip,brainwane/zulip,eeshangarg/zulip,andersk/zulip,tommyip/zulip,synicalsyntax/zulip,andersk/zulip,hackerkid/zulip,brainwane/zulip,rht/zulip,andersk/zulip,brainwane/zulip,hackerkid/zulip,punchagan/zulip,rishig/zulip,andersk/zulip,tommyip/zulip,timabbott/zulip,timabbott/zulip,shubhamdhama/zulip,showell/zulip,punchagan/zulip,andersk/zulip,zulip/zulip,synicalsyntax/zulip,kou/zulip,showell/zulip,zulip/zulip,kou/zulip,timabbott/zulip,hackerkid/zulip,tommyip/zulip,punchagan/zulip,shubhamdhama/zulip,rht/zulip,rht/zulip,brainwane/zulip,showell/zulip,hackerkid/zulip,rishig/zulip,hackerkid/zulip,rishig/zulip,eeshangarg/zulip,rishig/zulip,zulip/zulip,eeshangarg/zulip,timabbott/zulip,eeshangarg/zulip,synicalsyntax/zulip,shubhamdhama/zulip,kou/zulip,eeshangarg/zulip,synicalsyntax/zulip,zulip/zulip,kou/zulip,tommyip/zulip,rht/zulip,rht/zulip,shubhamdhama/zulip,punchagan/zulip,zulip/zulip,hackerkid/zulip,timabbott/zulip,punchagan/zulip,eeshangarg/zulip,shubhamdhama/zulip,shubhamdhama/zulip,rht/zulip,rishig/zulip,punchagan/zulip,andersk/zulip,kou/zulip,shubhamdhama/zulip,rishig/zulip,andersk/zulip,timabbott/zulip,zulip/zulip