* implement key config
* use key config in help component
* use key config in databases component
* use key config in error component
* use key config in connections component
* set commands
* use database/table as a table component name
* fix a test for get_text
* use key config in tab component
* fix function name
* add focus_connections key
* use quit exit key
* implement help compoment
* fix database filter
* add column types
* fix clippy warnings
* help scrolling
* panic if type is not implemented yet
* not panic but return error
* add decimal
* add a test for get_text
* fix clippy warnings
* select multiple cells
* define `expand_selected_area_x`, `expand_selected_area_y`
* make some table component fields private
* fix keymap
* fix a cell selection bug in page 2 and after
* add tests for `is_selected_cell` and `selected_cells`
* select cells while scrolling right
* calculate the number of cells considering cell spacing
* add tests for expand_selected_area
* add comments
* implement `reset`
* fix clippy warnings
Takayuki Maeda