Support beta client magic number convention

[aclist]

Thanks for this tool. It makes munging VDF data into a sane structure so much better.

As for the issue, dumping VDFs suddenly stopped working for me: it seems the magic number used by the VDF file fluctuates between two variants, 0x07564427 or 0x07564428.

Error: Custom { kind: InvalidInput, error: "Invalid magic number" }

Replacing line 6 in reader.rs with const MAGIC: u32 = 0x07564428; clears this, but I think the incoming format is slightly different in this case, so the parser fails at that point:

Error: Custom { kind: InvalidInput, error: "Couldn't parse VDF app section" }

You can see how SteamDB's tool conditionally switches between two parsing methods depending on which magic number is being used: https://github.com/SteamDatabase/SteamAppInfo/blob/master/SteamAppInfoParser/AppInfo.cs

Thanks in advance.

[aclist]

I did a bit more investigation and found that the 0x07564428 variant is tied to the beta client of Steam.