github files don't support emojies because it uses Base64 decoder that does not support it

[JensLincke]

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Describe the bug
A clear and concise description of what the bug is.

Saving and Loading drawio via github that contains emoji utf-8 unicode characters does not work, because it uses Base64 decode

To Reproduce
Steps to reproduce the behavior:

1. Try to load a file like:

<mxfile host="app.diagrams.net" agent="Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/139.0.0.0 Safari/537.36" version="28.1.2">
  <diagram name="Page-1" id="dGOvtMlQaf0YHdEt--z6">
    <mxGraphModel dx="1500" dy="915" grid="1" gridSize="10" guides="1" tooltips="1" connect="1" arrows="1" fold="1" page="1" pageScale="1" pageWidth="3000" pageHeight="1000" math="0" shadow="0">
      <root>
        <mxCell id="0" />
        <mxCell id="1" parent="0" />
        <mxCell id="MyRaAgb93ffFDz9J31C7-1" value="Text&amp;nbsp;👨‍" style="text;html=1;align=center;verticalAlign=middle;whiteSpace=wrap;rounded=0;" vertex="1" parent="1">
          <mxGeometry x="170" y="170" width="60" height="30" as="geometry" />
        </mxCell>
      </root>
    </mxGraphModel>
  </diagram>
</mxfile>

Reproduce it on a library level

// base64 encoded file
var content = 'PG14ZmlsZSBob3N0PSJhcHAuZGlhZ3JhbXMubmV0IiBhZ2VudD0iTW96aWxs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\nYW0+CjwvbXhmaWxlPgo=\n'

Base64.decode(content)
// produces garbage

<mxfile host="app.diagrams.net" agent="Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/139.0.0.0 Safari/537.36" version="28.1.2">
  <diagram name="Page-1" id="dGOvtMlQaf0YHdEt--z6">
    <mxGraphModel dx="1500" dy="915" grid="1" gridSize="10" guides="1" tooltips="1" connect="1" arrows="1" fold="1" page="1" pageScale="1" pageWidth="3000" pageHeight="1000" math="0" shadow="0">
      <root>
        <mxCell id="0" />
        <mxCell id="1" parent="0" />
        <mxCell id="MyRaAgb93ffFDz9J31C7-1" value="Text&amp;nbsp;ߑ袀�style="text;html=1;align=center;verticalAlign=middle;whiteSpace=wrap;rounded=0;" vertex="1" parent="1">
          <mxGeometry x="170" y="170" width="60" height="30" as="geometry" />
        </mxCell>
      </root>
    </mxGraphModel>
  </diagram>
</mxfile>
*/

Expected behavior
A clear and concise description of what you expected to happen.

Screenshots
If applicable, add screenshots to help explain your problem.

draw.io version (In the Help->About menu of the draw.io editor):

• draw.io version 28.1.2

Desktop (please complete the following information):

• OS: widows11
• Browser chrome
• Browser Version 139

I tested the problem in incognito/private mode with all browser extensions switched off, write "yes" below:

• no

Additional context
Add any other context about the problem here.

[JensLincke]

decoding emoji code:

function decodeB64Utf8(b64) {
  // 1) raw binary string (no UTF-8 step in your lib)
  const bin = Base64.decode(b64, true);
  // 2) binary string -> bytes
  const bytes = Uint8Array.from(bin, ch => ch.charCodeAt(0));
  // 3) proper UTF-8 decode
  return new TextDecoder('utf-8').decode(bytes);
}````

or 

fetch("data:text/plain;base64," + content).then(r => r.text())