invite: Focus first input in invite window in invite.js.
invite: Focus first input in invite window in invite.js.

Part of #16077.

eeshangarg/zulip,rht/zulip,zulip/zulip,andersk/zulip,punchagan/zulip,kou/zulip,hackerkid/zulip,zulip/zulip,rht/zulip,kou/zulip,rht/zulip,punchagan/zulip,rht/zulip,showell/zulip,punchagan/zulip,punchagan/zulip,showell/zulip,zulip/zulip,hackerkid/zulip,zulip/zulip,hackerkid/zulip,kou/zulip,punchagan/zulip,kou/zulip,hackerkid/zulip,eeshangarg/zulip,punchagan/zulip,showell/zulip,showell/zulip,kou/zulip,punchagan/zulip,andersk/zulip,rht/zulip,andersk/zulip,rht/zulip,andersk/zulip,eeshangarg/zulip,eeshangarg/zulip,showell/zulip,showell/zulip,hackerkid/zulip,hackerkid/zulip,kou/zulip,zulip/zulip,showell/zulip,andersk/zulip,hackerkid/zulip,zulip/zulip,rht/zulip,eeshangarg/zulip,zulip/zulip,eeshangarg/zulip,andersk/zulip,andersk/zulip,eeshangarg/zulip,kou/zulip