fix: Index out of range exception in Cheap Viewers rule

Need to generalize this and clean up the code later but this at least
fixes the immediate issue with the method.

Author: ProgrammingByPermutation

src/Nullinside.Api.TwitchBot.Tests/ChatRules/BestCheapViewersTests.cs

@@ -15,6 +15,8 @@ public class BestCheapViewersTests : AChatRuleUnitTestBase<BestCheapViewers> {
   /// </summary>
   /// <param name="badString">The string that should fail.</param>
   [Test]
+  [TestCase("C\u032dheap viewe\u034crs on\u0306 vwrpro.ru @8v2JcQFL")]
+  [TestCase("Ch\u031ae\u0345ap viewers on ***  @STGPMoLg")]
   [TestCase("Best\u036e vie\u0350wers \u0337on ***")]
   [TestCase("Best viewers on ***")]
   [TestCase("Best  viewers on ***")]

src/Nullinside.Api.TwitchBot.Tests/ChatRules/DoghypeTests.cs

@@ -15,6 +15,7 @@ public class DogehypeTests : AChatRuleUnitTestBase<Dogehype> {
   /// </summary>
   /// <param name="badString">The string that should fail.</param>
   [Test]
+  [TestCase("Visit dogehype dot com today and effortlessly boost your Twitch rankings!  @opAzPMVt")]
   [TestCase("Visit dogehype dot com and watch your channel grow today!  @5MGxTnYl")]
   [TestCase("Visit dogehype dot com today and climb the Twitch rankings with ease! Whether you're just starting out or looking to take your stream to the next level, DogeHype has the tools you need to succeed.  @gqznceDC")]
   [TestCase("Visit dogehype .biz com today and climb the Twitch rankings with ease! Whether you're just starting out or looking to take your stream to the next level, DogeHype has the tools you need to succeed.  @Axxq7ntz")]

src/Nullinside.Api.TwitchBot/ChatRules/BestCheapViewers.cs

@@ -47,7 +47,7 @@ public override async Task<bool> Handle(string channelId, ITwitchApiProxy botPro
         int offset = 0;
         for (int i = 0; i < expected.Length; i++) {
           // If this is a normal character it should be in the correct position.
-          if (normalized[i + offset] == expected[i]) {
+          if (i + offset < normalized.Length && normalized[i + offset] == expected[i]) {
             ++matches;
           } 
           // If this is an accent mark then the next character should match and the whole string we're evalutating