[FEATURE]: a feature to edit table and keep background color

[yu2chuan]

Is your feature request related to a problem? Please describe.
Users may copy a table with background color into linebyline. Currently, linebyline can show the background color. But after reopen the program, the background color of table wasn't saved successfully. Additionally, users can't add/delete rows/columns.

Describe the solution you'd like
The background color can be saved and kept. And users can add/delete rows/columns.

Describe alternatives you've considered
none

Additional context
If combining rows/columns can be supported, that will be great. But this request is to go too far.

[drl990114]

Good suggestion, but regarding saving the background color of the table, it seems that this feature can only be supported by parsing HTML. We will consider adding this feature in the future. #114