Hi there, I'm Matt Sergei (do call me Matt) and have the knowledge and skills to insert your Google text-to-speech box to your website (page).
Yet to achieve the same functionality as in Google Overview page (demo), this has to be done:
1. Cloud Platform project with enabled billing must be created/used with enabling Google Cloud Text-to-Speech API.
2. Set up authentication with a service account to get key credentials for using the API.
3. Creating the (console) application using Google Cloud Text-to-Speech Node.js Client, packing it to be used as a javascript library in the browser and then call that in the web page. For packing a module bundler called Webpack has to be used (I have some experience with it because I'm more using other ways or creating desktop apps with Node.js/Electron).
For #1 and #2 your project, billing and therefore API would be used (I can probably set up demo with my Google data).
For #3 the box you would like to use must be well specified since:
a. changes need to be made to the source code (console) app;
b. and then recompile the app each time;
c. to produce new javascript file.
With that there is considerable effort for all. My bid is my daily rate and I have added 2 days more for safety (and will not request more money). Since I'm incorporated I cannot bid for less.
If you agree with all I can start today since there is practically no work during this crisis. Otherwise I'm a webmaster for 26 years.
I hope you are safe and Regards,
Matt