bugdown/api_code_examples: Add macro for admin zuliprc lines.
bugdown/api_code_examples: Add macro for admin zuliprc lines.

Some of our code examples can only be run with administrator
credentials (such as create-user). Thus, the Markdown extension
for generating code examples should have an option to include
the lines that recommend using an admin zuliprc instead of a
non-admin one.

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