[FEATURE] Put up web page https://easyeyes.app/threshold

Created by: denispelli

PUT UP THE THRESHOLD PAGE. Let's implement the bare bones user interface of https://easyeyes.app/threshold/ . Create a threshold.html web page in the EasyEye.app directory. It should have the same menu bar as the rest of the pages in the easyeyes.app directory. For the time being, the common menu bar will NOT mention "Threshold". So the public won't easily find our page. I realize that Google will track it, but we don't need high security. Right now I imagine: • Menu bar, consistent with rest of EasyEyes.app • Easy uploading of a Threshold table to the EasyEyes directory. Uploading immediately begins the preprocessor. • A radio button selecting whether to run the preprocessor WITHOUT requiring a Pavlovia account. • A radio button selecting whether or not to enable automatic upload to Pavlovia. (Grayed out if scientist selected to run without pavlovia.) • Once the preprocessor runs, it should display a page of errors that can be saved to disk as a plain text file, possibly with Markdown formatting. • If and when the preprocessor finds no errors, and "automatic upload" is on, upload files to a new project in the scientist's Pavlovia account, and display a copyable display of the URL of the uploaded experiment. Label it: URL to run your uploaded experiment: • Note that any uploading to Pavlovia will require OAuth logging into Pavlovia. The preprocessor will check that any required consent forms and fonts are present in Pavlovia.

As a friendly gesture to visitors who may not yet have Pavlovia accounts, we offer the option of preprocessing WITHOUT Pavlovia to allow the scientist to see whatever error messages the preprocessor produces. However, we should NOT allow uploading to pavlovia until the preprocessor has checked the table's specified fonts and consents against those available in the EasyEyesResources folder of their Pavlovia site.