Add git help -w <help>

[kitarp29]

git help -w "command"

This is a git command, people can use to get all there is to know about a Git Command.
One just has to type git help -w '<'command'>' .This command will help the site to achieve, all the help one will ever need related to a command. Sweetest thing about this command is that this command opens a webpage in the browser and the pages are pre-downloaded and can be viewed even offline. There will no need to add anymore command specifically for each possible case in the first option.
I would love to work on this, if you guys want me to. I just need a green light and I will start working on it, will create a PR ASAP.

[kitarp29]

#82