shasum: add page

[alpreu]

---

• The page (if new), does not already exist in the repo.

• The page (if new), has been added to the correct platform folder:
  common/ if it's common to all platforms, linux/ if it's Linux-specific, and so on.

• The page has 8 or fewer examples.

• The PR is appropriately titled:
  <command name>: add page for new pages, or <command name>: <description of changes> for pages being edited

• The page follows the contributing guidelines

[agnivade]

Is this available on Windows too ? If not, then you should create separate entries in linux and osx folder. And remove this from common.

[alpreu]

@agnivade Oh sorry, I didn't quite understand that common included windows. I will create a new commit.

[agnivade]

It's mentioned in the PR template which you tick marked -

The page (if new), has been added to the correct platform folder:  
      `common/` if it's common to all platforms, `linux/` if it's Linux-specific, and so on.

Let me know if there is something that can be improved.

[sbrl]

Hey, thanks for the page! I've made a few comments on the linux version of the page, but they apply to both 😺

[sbrl]

Perhaps you could use the long form of the argument name here? So instead of -a use --algorithm?

[sbrl]

Same here.

[sbrl]

Typo: directorys -> directory's

[alpreu]

@sbrl I incorporated your comments :)
@agnivade I thought Common meant shared between osx and other *nixes. Maybe 'Crossplatform' might be a better term, or an explicit note that this includes Windows?

[sbrl]

@alpreu Thanks for the page 😺