Posssibility of using glob for filtering files when previewing

[andrecavallari]

Goals

1. More flexibility
2. More organized

Background

I'm currently using React Email in an existing project, which already has it's structure very well defined, but the templates are inside folders, together with other files that supports fetching external data or transforming data, so when I use the preview server, it's going to list every .tsx file inside all folders, so what we did is to create a folder named preview with all preview files inside so it wont list files like builder.tsx (wich is the one that builds the template using renderToString) and other files that we don't have preview, and unfortunately at this moment it's not possible to refactor the structure to match the React Email structure.

Proposal

Instead of using a --dir we could use --glob instead with a glob pattern to list all templates in a specific pattern.