Expand textExtensions with many missing common text file extensions
(.lua, .rb, .vue, .svelte, .dart, .tex, .scala, .lisp, and many more).
Add textFilenames list for well-known text files without a meaningful
extension (Makefile, Dockerfile, README, LICENSE, .gitignore, etc.)
so they open in the editor via handleEdit() instead of falling back
to xdg-open via handleOpenExternal().