Add OWML mod skeleton and import English translation template

Phase 2 (mod skeleton) + Phase 3 (import English source):

- manifest.json / SlovakTranslation.cs / ILocalizationAPI.cs registering
  "Slovenčina" via xen.LocalizationUtility (Interplanetary Polyglot).
- SlovakTranslation.csproj / .sln building net48 against the OWML and
  OuterWildsGameLibs NuGet packages — no game install needed to compile.
- assets/Translation.xml: English source template (896 KB, 2424 entries,
  keys == values) to be translated into Slovak.
- Project docs (README/PLAN/CLAUDE) and .gitignore.

Build verified: dotnet build -c Release stages a loadable mod folder.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

SlovakTranslation.sln

@@ -0,0 +1,22 @@
+
+Microsoft Visual Studio Solution File, Format Version 12.00
+# Visual Studio Version 16
+VisualStudioVersion = 16.0.30114.105
+MinimumVisualStudioVersion = 10.0.40219.1
+Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "SlovakTranslation", "SlovakTranslation.csproj", "{227A7B9F-9B05-4AE7-BDB9-1DE031C15853}"
+EndProject
+Global
+	GlobalSection(SolutionConfigurationPlatforms) = preSolution
+		Debug|Any CPU = Debug|Any CPU
+		Release|Any CPU = Release|Any CPU
+	EndGlobalSection
+	GlobalSection(SolutionProperties) = preSolution
+		HideSolutionNode = FALSE
+	EndGlobalSection
+	GlobalSection(ProjectConfigurationPlatforms) = postSolution
+		{227A7B9F-9B05-4AE7-BDB9-1DE031C15853}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{227A7B9F-9B05-4AE7-BDB9-1DE031C15853}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{227A7B9F-9B05-4AE7-BDB9-1DE031C15853}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{227A7B9F-9B05-4AE7-BDB9-1DE031C15853}.Release|Any CPU.Build.0 = Release|Any CPU
+	EndGlobalSection
+EndGlobal