Add a config load error troubleshooting

[craftzdog]

Under the "App won't launch" section.

Case 1: YAMLParseError

As of v5.6.0, the app converts the config file format from CSON to JSON.
When converting it but the data had a syntax error, YAML fails to parse it like so:

Failed to load `config.cson`
YAMLParseError: All mapping items must start at the same column at line 4, column 1:

            invalid: 1
    betaChannel: true
^

That's mostly due to invalid indentations mixed with spaces and tabs.

Case 2: JSON Syntax Error

Failed to load `config.json`
SyntaxError: Expected property name or '}' in JSON at position 15