minor: Export function `copy_handler`.
minor: Export function `copy_handler`.

This makes it potentially possible to call this function from other
code paths such as hotkeys.

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