Feature detection of web custom format support

[DavidMulder0]

Could we either allow

• a way to feature detect the support for specific mime types in write operations
• OR quietely ignore unsupported mime types as long as one is supported during a write operation

I was using the following code for mime type support feature detection

const isSupported = async (type) => {
        try {
          await navigator.clipboard.write([
            new ClipboardItem({
              [type]: new Blob(["test content for " + type], { type }),
            }),
          ]);
          return true;
        } catch (e) {
          return false;
        }
};

but this causes issues in Chrome and Edge: https://bugs.chromium.org/p/chromium/issues/detail?id=1509827

Additionally writing to the clipboard just to see whether it will fail is... not pretty.

[DavidMulder0]

Duplicate of #170 , apologies