Update "By" text casing in MainLayout.razor for consistency

Author: SamProf

src/MatBlazor.Demo/Shared/MainLayout.razor

@@ -27,7 +27,7 @@
                     <i class="fa fa-github" aria-hidden="true"></i>
                 </MatIconButton>
                 <a href="https://www.samprof.com" target="_blank" style="white-space: nowrap;" class="brand-link">
-                    By SamProf
+                    by SamProf
                 </a>
             </MatHidden>
             <MatHidden BreakPoint="@MatBreakpoint.SM" Direction="@MatHiddenDirection.Up">