api - update watcher docs
api - update watcher docs

//cc @lszomoru

microsoft/vscode,eamodio/vscode,eamodio/vscode,eamodio/vscode,eamodio/vscode,microsoft/vscode,eamodio/vscode,microsoft/vscode,eamodio/vscode,microsoft/vscode,eamodio/vscode,eamodio/vscode,microsoft/vscode,microsoft/vscode,microsoft/vscode,microsoft/vscode,microsoft/vscode,eamodio/vscode,microsoft/vscode,eamodio/vscode,eamodio/vscode,microsoft/vscode,eamodio/vscode,eamodio/vscode,eamodio/vscode,microsoft/vscode,microsoft/vscode,microsoft/vscode,microsoft/vscode,eamodio/vscode,microsoft/vscode,microsoft/vscode,eamodio/vscode,eamodio/vscode