Edit command as user OS config option

[caojoshua]

Adding os.editCommand as an optional user config, similar to os.openCommand. If omitted in the config, falls back to the previous options. If included in the config, run {{os.openCommand}} {{filename}}.

Testing

• Fedora Linux
• Empty config / config without os.editCommand
• config including os.editCommand = nano, vim, etc.

Caveats

• New to go programming language, so not sure about code quality, especially the testing code
• I added empty default configurations for non-Linux, but only have a Linux machine to test on

Docs

I haven't wrote any docs, but if the maintainers decide this is a desired feature, I can draft something up. To my knowledge, there currently is not any sections that describes how lazygit chooses the text editor for editCommand, so maybe I could add a section on that in Config.md.

[jesseduffield]

Looks good :) Just one thing, could we update config.md accordingly?

[caojoshua]

Looks good :) Just one thing, could we update config.md accordingly?

done in most recent commit.

[jesseduffield]

Suggested change

	### EditCommand
	### Configuring File Editing

Slightly more domain-specific title

[caojoshua]

Made the change, along with some better English in that section.

[jesseduffield]

one more thing!

[jesseduffield]

LGTM! Made a couple minor changes to the wording, but otherwise all good