Add screenshot to README
Add screenshot to README

joshblum/eeg-toolkit,joshblum/eeg-toolkit,joshblum/eeg-spectrogram,joshblum/eeg-spectrogram,joshblum/eeg-toolkit,joshblum/eeg-spectrogram,joshblum/eeg-spectrogram,joshblum/eeg-toolkit,joshblum/eeg-toolkit,joshblum/eeg-spectrogram