emscripten: Add a few keyCode mappings for German keyboards

From @sy2002 in https://github.com/emscripten-ports/SDL2/issues/108

src/video/emscripten/SDL_emscriptenevents.c

@@ -103,10 +103,10 @@ static const SDL_Scancode emscripten_scancode_table[] = {
     /*  57 */   SDL_SCANCODE_9,
     /*  58 */   SDL_SCANCODE_UNKNOWN,
     /*  59 */   SDL_SCANCODE_SEMICOLON,
-    /*  60 */   SDL_SCANCODE_UNKNOWN,
+    /*  60 */   SDL_SCANCODE_NONUSBACKSLASH,
     /*  61 */   SDL_SCANCODE_EQUALS,
     /*  62 */   SDL_SCANCODE_UNKNOWN,
-    /*  63 */   SDL_SCANCODE_UNKNOWN,
+    /*  63 */   SDL_SCANCODE_MINUS,
     /*  64 */   SDL_SCANCODE_UNKNOWN,
     /*  65 */   SDL_SCANCODE_A,
     /*  66 */   SDL_SCANCODE_B,
@@ -203,7 +203,7 @@ static const SDL_Scancode emscripten_scancode_table[] = {
     /* 157 */   SDL_SCANCODE_UNKNOWN,
     /* 158 */   SDL_SCANCODE_UNKNOWN,
     /* 159 */   SDL_SCANCODE_UNKNOWN,
-    /* 160 */   SDL_SCANCODE_UNKNOWN,
+    /* 160 */   SDL_SCANCODE_GRAVE,
     /* 161 */   SDL_SCANCODE_UNKNOWN,
     /* 162 */   SDL_SCANCODE_UNKNOWN,
     /* 163 */   SDL_SCANCODE_KP_HASH, /*KaiOS phone keypad*/
@@ -214,7 +214,7 @@ static const SDL_Scancode emscripten_scancode_table[] = {
     /* 168 */   SDL_SCANCODE_UNKNOWN,
     /* 169 */   SDL_SCANCODE_UNKNOWN,
     /* 170 */   SDL_SCANCODE_KP_MULTIPLY, /*KaiOS phone keypad*/
-    /* 171 */   SDL_SCANCODE_UNKNOWN,
+    /* 171 */   SDL_SCANCODE_RIGHTBRACKET,
     /* 172 */   SDL_SCANCODE_UNKNOWN,
     /* 173 */   SDL_SCANCODE_MINUS, /*FX*/
     /* 174 */   SDL_SCANCODE_VOLUMEDOWN, /*IE, Chrome*/