The site detects .ts files as what I presume are TypeScript documents, but the file extension can also apply to the "MPEG transport stream (MPEG-TS, MTS) or simply transport stream (TS)" container format. For file extensions that can have multiple purposes like this, the site could use an "if then" so the user can select what type of document it is, or the site can read the file and determine it based on the content.