Update README.md to provide additional configuration guidance

[morganarnel]

The Readme currently contains the following guidance

Configure PHPStorm
We've received feedback that PHPStorm IDE default file size is too small to load the AccountingApi class.

"PHPStorm seems unable to resolve the XeroAPI\XeroPHP\Api\AccountingApi class. It just shows Undefined class 'AccountingApi' and therefore can't autocomplete any of the methods etc."

To fix this, add the following to the idea.properties file to increase this limit to 5000 kilobytes

idea.max.intellisense.filesize=5000

Instructions here for configuring PHPStorm platform properties on Mac/Windows/Linux

Suggestion is to also add additional guidance for those using PHP Intelephense with Visual Studio Code, suggesting that they increase their maximum file size to 3000000 bytes in Settings -> Extensions -> Intelephense -> Files: Max Size.

OR

just abstract some things out 🤷

It's more than possible that increasing these settings in larger projects (projects integrating with Xero tend to be) could cause some serious slowdown issues in the background when it comes to indexing and such. Then you shouldn't need to provide any of this guidance.

[morganarnel]

I mean, even GitHub stops people from viewing it as it's too large.