implement osu!taiko diffcalc

[Hiviexd]

not really sure if this is even possible with a plugin but i remain hopeful

lack of taiko diffcalc is causing the issue where diffs with custom names are always marked as "Easy", which causes an insane amount of false positives, so users have to manually change that to the correct diff, which isn't intuitive nor optimal.

[hongaaronc]

talked briefly with Alchyr and was advised to probably look at the lazer code for the SR calculation:
https://github.com/ppy/osu/blob/master/osu.Game.Rulesets.Taiko/Difficulty/TaikoDifficultyCalculator.cs

I think it should be possible but not completely sure. will have to look into it a bit more

[hongaaronc]

Plan is to implement diffcalc the proper way, by putting it in MapsetParser. Naxess is willing to do another release if we do the implementation/submit a PR.

Instructions for setting up and installing MapsetParser with hardcoded "Expert" as default:

1. Clone https://github.com/Naxesss/MapsetParser or a fork to a local repo
2. Open <MP directory>/MapsetParser.csproj in Visual Studio
3. Open <MP directory>/objects/Beatmap.cs, add to line 515: difficulty = Difficulty.Expert;
4. Go to Build > Build Solution and Build > Build MapsetParser
5. This will produce a DLL file: <MP directory>/bin/Debug/netcoreapp3.1/MapsetParser.dll
6. Open Mapset Verifier, go to Settings > Shortcuts > Open Application Folder
7. Drag the newly built MapsetParser.dll into <MV App Folder>/api/win-x86

As far as diffcalc implementation goes, it looks like the interfaces for MapsetVerifier that Naxess made are super similar to the lazer ones, so migration should be pretty close to 1:1. We should also be sure to keep the lazer license intact.

[hongaaronc]

soon ™️
Naxesss/MapsetParser#12