user docs: Update create-a-stream to point to the org guide on streams.
user docs: Update create-a-stream to point to the org guide on streams.

Also cleans up the intro a bit.

rht/zulip,showell/zulip,mahim97/zulip,brockwhittaker/zulip,dhcrzf/zulip,shubhamdhama/zulip,punchagan/zulip,dhcrzf/zulip,zulip/zulip,showell/zulip,eeshangarg/zulip,kou/zulip,synicalsyntax/zulip,mahim97/zulip,shubhamdhama/zulip,rht/zulip,hackerkid/zulip,mahim97/zulip,showell/zulip,eeshangarg/zulip,zulip/zulip,showell/zulip,timabbott/zulip,showell/zulip,hackerkid/zulip,rishig/zulip,shubhamdhama/zulip,andersk/zulip,dhcrzf/zulip,andersk/zulip,synicalsyntax/zulip,shubhamdhama/zulip,Galexrt/zulip,synicalsyntax/zulip,punchagan/zulip,timabbott/zulip,brainwane/zulip,brainwane/zulip,timabbott/zulip,punchagan/zulip,eeshangarg/zulip,brockwhittaker/zulip,punchagan/zulip,rishig/zulip,shubhamdhama/zulip,brockwhittaker/zulip,zulip/zulip,tommyip/zulip,tommyip/zulip,brainwane/zulip,tommyip/zulip,synicalsyntax/zulip,Galexrt/zulip,eeshangarg/zulip,tommyip/zulip,hackerkid/zulip,rht/zulip,brainwane/zulip,rishig/zulip,brainwane/zulip,brainwane/zulip,Galexrt/zulip,hackerkid/zulip,synicalsyntax/zulip,brainwane/zulip,timabbott/zulip,andersk/zulip,jackrzhang/zulip,jackrzhang/zulip,rht/zulip,mahim97/zulip,rishig/zulip,Galexrt/zulip,kou/zulip,eeshangarg/zulip,andersk/zulip,kou/zulip,synicalsyntax/zulip,timabbott/zulip,zulip/zulip,showell/zulip,kou/zulip,timabbott/zulip,jackrzhang/zulip,eeshangarg/zulip,showell/zulip,kou/zulip,zulip/zulip,eeshangarg/zulip,andersk/zulip,dhcrzf/zulip,jackrzhang/zulip,Galexrt/zulip,jackrzhang/zulip,synicalsyntax/zulip,brockwhittaker/zulip,timabbott/zulip,Galexrt/zulip,hackerkid/zulip,mahim97/zulip,mahim97/zulip,shubhamdhama/zulip,jackrzhang/zulip,dhcrzf/zulip,rishig/zulip,punchagan/zulip,brockwhittaker/zulip,zulip/zulip,punchagan/zulip,andersk/zulip,hackerkid/zulip,rishig/zulip,zulip/zulip,hackerkid/zulip,punchagan/zulip,kou/zulip,tommyip/zulip,dhcrzf/zulip,Galexrt/zulip,rht/zulip,shubhamdhama/zulip,rishig/zulip,dhcrzf/zulip,tommyip/zulip,tommyip/zulip,andersk/zulip,kou/zulip,jackrzhang/zulip,rht/zulip,rht/zulip,brockwhittaker/zulip