For plot functions, add plots for standardized changes

[sfcheung]

To-Do

• [X] List the plot functions involved. (Write new functions)
• [x] Revise the functions or add new functions if necessary.

Status

Working in this branch: plot_est_change.

Note

• For raw changes, (e.g., est_change_raw()), gCD values are not available. Index plots will be used.

[sfcheung]

Done in https://github.com/sfcheung/semfindr/pull/66