Send inline image attchment in Node-RED pushover message

The documentation for the node red pushover node for using attachments was not very detailed, only "Buffer containing image".

Follow these simple steps in a "function" node to add an image attachment as buffered data.

1. Convert your image to base64,  https://www.base64-image.de/
2. Remove initial metadata from base64, e.g:

   data:image/webp;base64,

3.  Set attachment data:

   var attachmentBase64 = "<string from step 2>"

4. Add this to the function node where you format your pushover message:

   msg.attachment = Buffer.from(attachmentBase64, 'utf8');