static/js/compose.js: Clean `add_markdown` function.
static/js/compose.js: Clean `add_markdown` function.

Rename `add_markdown` function to `wrap_text_with_markdown` and
use closure variables in function `wrap_text_with_markdown`.

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