Add reference to some builtin fixtures in "contents"
Add reference to some builtin fixtures in "contents"

Fix #1408

nicoddemus/pytest,lukas-bednar/pytest,tomviner/pytest,RonnyPfannschmidt/pytest,eli-b/pytest,omarkohl/pytest,vodik/pytest,tgoodlet/pytest,tareqalayan/pytest,flub/pytest,ddboline/pytest,alfredodeza/pytest,userzimmermann/pytest,JonathonSonesen/pytest,userzimmermann/pytest,tomviner/pytest,rmfitzpatrick/pytest,nicoddemus/pytest,MichaelAquilina/pytest,MengJueM/pytest,hackebrot/pytest,vodik/pytest,Akasurde/pytest,pytest-dev/pytest,hpk42/pytest,vmalloc/dessert,Bachmann1234/pytest,txomon/pytest,ropez/pytest,ropez/pytest,etataurov/pytest,JonathonSonesen/pytest,The-Compiler/pytest,skylarjhdownes/pytest,pfctdayelise/pytest,omarkohl/pytest,The-Compiler/pytest,hpk42/pytest,jaraco/pytest,Bachmann1234/pytest,malinoff/pytest,MengJueM/pytest,markshao/pytest,lukas-bednar/pytest,davidszotten/pytest