[docs] Add exemplar project to solution (#5650)

OpenTelemetry.sln

@@ -336,6 +336,8 @@ Project("{2150E333-8FDC-42A3-9474-1A3956D46DE8}") = "scripts", "scripts", "{4498
 		build\scripts\update-changelogs.ps1 = build\scripts\update-changelogs.ps1
 	EndProjectSection
 EndProject
+Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "exemplars", "docs\metrics\exemplars\exemplars.csproj", "{79C12C80-B27B-41FB-AE79-A3BB74CFA782}"
+EndProject
 Global
 	GlobalSection(SolutionConfigurationPlatforms) = preSolution
 		Debug|Any CPU = Debug|Any CPU
@@ -590,6 +592,10 @@ Global
 		{19545B37-8518-4BDD-AD49-00C031FB3C2A}.Debug|Any CPU.Build.0 = Debug|Any CPU
 		{19545B37-8518-4BDD-AD49-00C031FB3C2A}.Release|Any CPU.ActiveCfg = Release|Any CPU
 		{19545B37-8518-4BDD-AD49-00C031FB3C2A}.Release|Any CPU.Build.0 = Release|Any CPU
+		{79C12C80-B27B-41FB-AE79-A3BB74CFA782}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{79C12C80-B27B-41FB-AE79-A3BB74CFA782}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{79C12C80-B27B-41FB-AE79-A3BB74CFA782}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{79C12C80-B27B-41FB-AE79-A3BB74CFA782}.Release|Any CPU.Build.0 = Release|Any CPU
 	EndGlobalSection
 	GlobalSection(SolutionProperties) = preSolution
 		HideSolutionNode = FALSE
@@ -647,6 +653,7 @@ Global
 		{87A20A76-D524-4AAC-AF92-8725BFED0415} = {A49299FB-C5CD-4E0E-B7E1-B7867BBD67CC}
 		{993E65E5-E71B-40FD-871C-60A9EBD59724} = {A49299FB-C5CD-4E0E-B7E1-B7867BBD67CC}
 		{44982E0D-C8C6-42DC-9F8F-714981F27CE6} = {7CB2F02E-03FA-4FFF-89A5-C51F107623FD}
+		{79C12C80-B27B-41FB-AE79-A3BB74CFA782} = {3277B1C0-BDFE-4460-9B0D-D9A661FB48DB}
 	EndGlobalSection
 	GlobalSection(ExtensibilityGlobals) = postSolution
 		SolutionGuid = {55639B5C-0770-4A22-AB56-859604650521}