move markdown-spellcheck installation to the install section
move markdown-spellcheck installation to the install section

PaulHigin/PowerShell,PaulHigin/PowerShell,TravisEz13/PowerShell,JamesWTruher/PowerShell-1,TravisEz13/PowerShell,daxian-dbw/PowerShell,PaulHigin/PowerShell,TravisEz13/PowerShell,daxian-dbw/PowerShell,PaulHigin/PowerShell,daxian-dbw/PowerShell,JamesWTruher/PowerShell-1,JamesWTruher/PowerShell-1,TravisEz13/PowerShell,daxian-dbw/PowerShell,JamesWTruher/PowerShell-1