clien: pdf-gen: load logo externally; add prepare step * Change the way how the logo to be placed in the pdf is loaded: It can be configured in the `.env.local´ file, otherwise a placeholder will be loaded from the static assets. The placeholder has not been placed in `assets` because it won't be needed if a real logo has been specified and thus should not compiled in by default. * Add a mechanism to do asynchronous preparations before rendering. This is needed for the completeion of the Image() loading, but it also shows how asynchronous preparational step can be added in principle. * Disable the start button when the current rendering is in progress.

#Name of the application, e.g. displayed at login time
VUE_APP_TITLE=Waterway Monitoring system

#Backend URL
VUE_APP_API_URL=/api/
VUE_BACKEND_API_URL=http://gemma_backend:8000

#Path of vendored images is copied during a webpack build
VUE_APP_VENDOR_IMG_PATH=

#Logos to be potentially loaded by the SPA. Can be left blank.
VUE_APP_SECONDARY_LOGO_URL=
VUE_APP_LOGO_FOR_PDF_URL=