Add API documentation to README.
Add API documentation to README.

b1tw1se/sidetiq,endofunky/sidetiq,tobiassvn/sidetiq,slategroup/sidetiq,grzlus/sidetiq,talentpad/sidetiq,atpay/sidetiq,danilogcarolino/sidetiq,endofunky/sidetiq,slategroup/sidetiq,flowerett/sidetiq,stanchan/sidetiq,talentpad/sidetiq,PaulMest/sidetiq,Altonymous/sidetiq,sfroehler/sidetiq,kickserv/sidetiq,vayu-technology/sidetiq,danilogcarolino/sidetiq,atpay/sidetiq,vayu-technology/sidetiq,rjocoleman/sidetiq,kickserv/sidetiq,tomoyuki-yanagisawa/sidetiq-mod,b1tw1se/sidetiq,akhiln/sidetiq,tomoyuki-yanagisawa/sidetiq-mod,stanchan/sidetiq,brennovich/sidetiq,PaulMest/sidetiq,brennovich/sidetiq,sfroehler/sidetiq,akhiln/sidetiq,flowerett/sidetiq,rjocoleman/sidetiq,tobiassvn/sidetiq,grzlus/sidetiq