add partly local manual support

[asukaminato0721]

Is your feature request related to a problem?

Currently, it will only go to the online manual, which is slow. If local has manual, prefer local will be much faster.

Describe the solution you'd like

Suppose the help docs are under the ~/path/to/docs/, if we want to find something like Function

for *nix user.

find ~/path/to/docs/ -name Function.nb -exec wolframplayer {} +

the wolframplayer is distributed with the free Wolfram engine.

will do the trick. But I am not sure it could execute in vscode.

the variable pathToDocs could be set in the setting.

Additional context Add any other context or screenshots about the feature request here.

[asukaminato0721]

https://github.com/wuyudi/mmaf1 I write a very simple PoC extension, which works.