Resources refuses two kinds of file, and everything else is allowed. The refusal is immediate, before any of the file is sent, and it names the extension: .svg files are not allowed in project resources.
Programs and installers: .exe, .dll, .so, .dylib, .bat, .cmd, .com, .msi, .scr, .jar, .app, .deb, .rpm, .sh, .ps1, .vbs
Anything a browser would run rather than show: .html, .htm, .xhtml, .shtml, .svg, .svgz, .xml, .xsl, .xslt, .js, .mjs, .mhtml, .swf
Everything not on those two lists goes through. PDF, ZIP, DWG, DXF, RVT, SKP, 3DM, IFC, PSD, AI, INDD, XLSX, DOCX, MP4, PNG, JPEG and TIFF are all fine.
SVG is the one that catches designers
It is worth saying plainly, because it is by far the most common refusal here: SVG will never upload to Resources. An SVG is not only a drawing, it is a document that can carry scripts, and a file served straight from storage with its real type would run those scripts. The same reasoning covers .html, .js and .xml.
The same rule applies to project media, so exporting to PNG or PDF is the answer in both places. Why a file was refused when adding media to a project covers the media side, which has its own separate and much shorter list of accepted formats.
Put blocked files inside a ZIP
A ZIP is accepted, and the check only reads the extension of the file you upload, not what is inside it. So a web export, an SVG set or a script folder can be zipped and uploaded as one archive. Whoever downloads it unzips it on their own machine, which is exactly what the rule is designed to force.
Size is a separate check
Any single file must be under 2 GB, whatever its type. Over that you get File is larger than the 2 GB limit. That is per file: the project's total allowance is a different limit again, and it depends on membership. See Resources storage limits and how to free space.
Importing from Google Drive has a lower ceiling than uploading directly: see Importing files from Google Drive into Resources.
Renaming the extension will not help
Changing report.html to report.txt gets past the extension check, and it also means nobody who downloads it can open it as intended. Zip it instead.