docs: Add a quick start guide

[gaocegege]

We could provide a quick start, giving a simple Alipay/Wechat fake records, and explain how to write config rules for it.

Ref https://github.com/deb-sig/double-entry-generator/issues/151#issuecomment-2781818117

[rennsax]

I'd like to report one point that may upset new users:

double-entry-generator translate --provider wechat --config no-file.yml ~/Downloads/wechat.csv

When the configuration file does not exist and the account file does exist, the following error message is emitted:

2025/04/07 09:50:00 Failed to get default options in config

which is a little bit ... overwhelmed. A user may wonder that what is a "config" and why the program fails to get the "default options"? (I did when I was a newbie.) We can provide more user-friendly error message in this case, such as "warning/error: the config file no-file.yml does not exist".

[Triple-Z]

Maybe the examples/ is a good starting point.

[TerrySolar]

应该是这个快速上手的参数配置已经落后了，我也是用了这个示例发现报错了