Expression atlas downloader

[enriquea]

Actions to improve the current expression atlas downloader:

• Include missing file in configuration: Ensure the <accession>-transcripts-tpms.tsv file is explicitly listed in the configuration JSON.
• Add download progress indicator: Currently, downloads occur without user feedback. Implement a clear progress bar to display download status.
• Restrict downloads to essential files: Consider limiting downloads to only the necessary files by default—even when no configuration file is specified.