grub-editenv: add page

[SAYUK09]

• The page(s) are in the correct platform directories: common, linux, osx, windows, sunos, android, etc.
• The page(s) have at most 8 examples.
• The page description(s) have links to documentation or a homepage.
• The page(s) follow the content guidelines.
• The PR title conforms to the recommended templates.

[CLAassistant]

All committers have signed the CLA.

[Magrid0]

Hi, thanks for contributing to this project, but unfortunately we can't accept this pull request, we advise to take a look to the style guide and update the file.

[SAYUK09]

Hi, thanks for contributing to this project, but unfortunately we can't accept this pull request, we advise to take a look to the style guide and update the file.

I have made the changes. Please take a look now.
Thanks @Magrid0

[Magrid0]

it's still not correct

[Magrid0]

with this last change it should pass the check

[SAYUK09]

Thanks for helping our @kbdharun

[kbdharun]

LGTM, Welcome to tldr and thanks for your contribution.

[Magrid0]

Looks good to me, thanks for your contribution!