readme tweaks

Author: lerouxb

packages/browser-repl/README.md

@@ -34,8 +34,8 @@ Shell is a React component with the following properties:
 - `onOutputChanged?: (output: ShellOutputEntry[]) => void`: A function called each time the output changes with an array of `ShellOutputEntries`.
 - `onHistoryChanged?: (history: string[]) => void`: A function called each time the history changes with an array of history entries ordered from the most recent to the oldest entry.
 - `onEditorChanged?: (editor: EditorRef | null) => void`: A function called each time the editor ref changes. Can be used to call editor methods.
-- `onOperationStarted: () => void`: A function called when an operation has begun.
-- `onOperationEnd: () => void`: A function called when an operation has completed (both error and success).
+- `onOperationStarted?: () => void`: A function called when an operation has begun.
+- `onOperationEnd?: () => void`: A function called when an operation has completed (both error and success).
 - `redactInfo?: boolean`: If set, the shell will omit or redact entries containing sensitive info from history. Defaults to `false`.
 - `maxOutputLength?: number`: The maxiumum number of lines to keep in the output. Defaults to `1000`.
 - `maxHistoryLength?: number`: The maxiumum number of lines to keep in the history. Defaults to `1000`.