DotenvEditor::format() should quotes values when they contain certain characters

[pointybeard]

When exporting a .env file, values are never wrapped in quotes. When a value contains certain characters, like =, $, or \n (new line), this causes the resultant contents to be invalid.

E.g.

<?php

use sixlive\DotenvEditor\DotenvEditor;

include "vendor/autoload.php";

$editor = new DotenvEditor;

$editor->load(__DIR__.'/.env');

$editor->heading('Examples');
$editor->set('A', 't9maWr2GA6=');
$editor->set('B', 'this-should-be-$ingle-quoted');
$editor->set('C', 'multi
line
should be
quoted');

$editor->save();

Results in

# Examples
A=t9maWr2GA6=
B=this-should-be-$ingle-quoted
C=multi
line
should be
quoted

This is not a valid dotenv file and, for example, Laravel will not be able to load it.

https://github.com/sixlive/dotenv-editor/blob/edf0a7523fd2c49a435feffad7524ad60475cb47/src/DotenvEditor.php#L155

There needs to be some different preparation of values, that need quoting, prior to writing them to the .env file.

For example:

1. If contains =, #, or a $ as part of variable/command substitution (e.g. "$(bleh)" or "${FOO}") then wrap in double quotes
2. If contains $ not used for variable/command substitution, then wrap in single quotes
3. If contains new line character (\n) either wrap in double quotes and\or convert the new line characters to a \n literal string

[sixlive]

This is definitely something that should be implemented. Would you be willing work open a PR for this?