refactor: add new constants & reuse

Author: xeho91

src/constants.ts

@@ -1,4 +1,6 @@
 export const SVELTE_CSF_TAG_PREFIX = 'svelte-csf';
 export const SVELTE_CSF_V4_TAG = `${SVELTE_CSF_TAG_PREFIX}-v4`;
 export const SVELTE_CSF_V5_TAG = `${SVELTE_CSF_TAG_PREFIX}-v5`;
-export const STORYBOOK_META_IDENTIFIER = '$__meta';
+export const STORYBOOK_INTERNAL_PREFIX = '$__';
+export const STORYBOOK_META_IDENTIFIER = `${STORYBOOK_INTERNAL_PREFIX}meta`;
+export const RUNTIME_STORIES_IDENTIFIER = `${STORYBOOK_INTERNAL_PREFIX}stories`;