Added more intro content in the mechanics docs.
Added more intro content in the mechanics docs.

toolforger/sympy,moble/sympy,abhiii5459/sympy,lidavidm/sympy,shikil/sympy,maniteja123/sympy,sampadsaha5/sympy,debugger22/sympy,hrashk/sympy,madan96/sympy,liangjiaxing/sympy,Arafatk/sympy,skirpichev/omg,ga7g08/sympy,jaimahajan1997/sympy,cswiercz/sympy,kaushik94/sympy,hargup/sympy,ChristinaZografou/sympy,pbrady/sympy,ahhda/sympy,Gadal/sympy,AkademieOlympia/sympy,moble/sympy,abloomston/sympy,souravsingh/sympy,grevutiu-gabriel/sympy,atsao72/sympy,jaimahajan1997/sympy,Mitchkoens/sympy,asm666/sympy,dqnykamp/sympy,kevalds51/sympy,wyom/sympy,VaibhavAgarwalVA/sympy,drufat/sympy,shipci/sympy,kevalds51/sympy,abloomston/sympy,Gadal/sympy,souravsingh/sympy,postvakje/sympy,dqnykamp/sympy,saurabhjn76/sympy,mafiya69/sympy,Davidjohnwilson/sympy,AunShiLord/sympy,grevutiu-gabriel/sympy,atreyv/sympy,ga7g08/sympy,MechCoder/sympy,Curious72/sympy,pandeyadarsh/sympy,toolforger/sympy,jbbskinny/sympy,Arafatk/sympy,aktech/sympy,drufat/sympy,sahilshekhawat/sympy,kumarkrishna/sympy,amitjamadagni/sympy,Titan-C/sympy,ga7g08/sympy,jerli/sympy,AunShiLord/sympy,sahilshekhawat/sympy,sahmed95/sympy,Shaswat27/sympy,sahilshekhawat/sympy,drufat/sympy,MechCoder/sympy,Mitchkoens/sympy,Sumith1896/sympy,saurabhjn76/sympy,chaffra/sympy,AkademieOlympia/sympy,wanglongqi/sympy,jaimahajan1997/sympy,aktech/sympy,mafiya69/sympy,liangjiaxing/sympy,oliverlee/sympy,Gadal/sympy,kaichogami/sympy,MridulS/sympy,mafiya69/sympy,bukzor/sympy,garvitr/sympy,kmacinnis/sympy,MechCoder/sympy,yashsharan/sympy,MridulS/sympy,kumarkrishna/sympy,iamutkarshtiwari/sympy,skidzo/sympy,iamutkarshtiwari/sympy,Sumith1896/sympy,asm666/sympy,Vishluck/sympy,Curious72/sympy,kevalds51/sympy,jamesblunt/sympy,liangjiaxing/sympy,Arafatk/sympy,maniteja123/sympy,rahuldan/sympy,Davidjohnwilson/sympy,AkademieOlympia/sympy,grevutiu-gabriel/sympy,sampadsaha5/sympy,cccfran/sympy,jerli/sympy,amitjamadagni/sympy,cccfran/sympy,kaichogami/sympy,Vishluck/sympy,shikil/sympy,wyom/sympy,meghana1995/sympy,beni55/sympy,jbbskinny/sympy,Shaswat27/sympy,emon10005/sympy,iamutkarshtiwari/sympy,jerli/sympy,skidzo/sympy,kmacinnis/sympy,garvitr/sympy,Titan-C/sympy,atreyv/sympy,jamesblunt/sympy,jamesblunt/sympy,mcdaniel67/sympy,Curious72/sympy,yukoba/sympy,meghana1995/sympy,yashsharan/sympy,pandeyadarsh/sympy,lidavidm/sympy,rahuldan/sympy,meghana1995/sympy,wyom/sympy,vipulroxx/sympy,pbrady/sympy,asm666/sympy,lidavidm/sympy,postvakje/sympy,emon10005/sympy,dqnykamp/sympy,lindsayad/sympy,skidzo/sympy,farhaanbukhsh/sympy,souravsingh/sympy,sunny94/temp,kmacinnis/sympy,jbbskinny/sympy,sampadsaha5/sympy,cccfran/sympy,rahuldan/sympy,atreyv/sympy,VaibhavAgarwalVA/sympy,Designist/sympy,Mitchkoens/sympy,yukoba/sympy,aktech/sympy,kaichogami/sympy,Titan-C/sympy,sunny94/temp,garvitr/sympy,sunny94/temp,beni55/sympy,atsao72/sympy,farhaanbukhsh/sympy,oliverlee/sympy,wanglongqi/sympy,cswiercz/sympy,hargup/sympy,maniteja123/sympy,abloomston/sympy,lindsayad/sympy,pandeyadarsh/sympy,debugger22/sympy,hargup/sympy,abhiii5459/sympy,Vishluck/sympy,vipulroxx/sympy,atsao72/sympy,abhiii5459/sympy,farhaanbukhsh/sympy,sahmed95/sympy,Shaswat27/sympy,shikil/sympy,bukzor/sympy,postvakje/sympy,toolforger/sympy,ahhda/sympy,madan96/sympy,kaushik94/sympy,chaffra/sympy,mcdaniel67/sympy,Designist/sympy,kumarkrishna/sympy,debugger22/sympy,hrashk/sympy,ahhda/sympy,shipci/sympy,yashsharan/sympy,pbrady/sympy,bukzor/sympy,Designist/sympy,saurabhjn76/sympy,ChristinaZografou/sympy,ChristinaZografou/sympy,Sumith1896/sympy,mcdaniel67/sympy,Davidjohnwilson/sympy,MridulS/sympy,cswiercz/sympy,AunShiLord/sympy,diofant/diofant,lindsayad/sympy,oliverlee/sympy,beni55/sympy,wanglongqi/sympy,madan96/sympy,emon10005/sympy,VaibhavAgarwalVA/sympy,chaffra/sympy,yukoba/sympy,sahmed95/sympy,vipulroxx/sympy,kaushik94/sympy,shipci/sympy,hrashk/sympy,moble/sympy