Replace `.callgraphignore` by settings

[beicause]

The design of using.callgraphignore to ignore specific files is not good and not intuitive. Unless read the README carefully, users can't think of using it (#33).

I suggest moving it to the settings, they can have both inclusion and exclusion and don't limit the searching path to workspace ( see #17 ). For individual projects, it can also be set in .vscode/seting.json