The Page TSConfig which is normally stored in a field in the root page can be moved to the file Configuration/TSConfig/Page.ts .
In order to load this a line needs to be added to ext_tables.php :
'<INCLUDE_TYPOSCRIPT: source="FILE:EXT:' . $_EXTKEY . '/Configuration/TSConfig/Page.ts">'
Although the actual TSConfig could be included in ext_tables.php it's of course easier for maintenance to have it in a separate file.
In a similar way it's possible to load user TSConfig (