fix: allow to omit region name in endregion tag in code snippets (#1909)

* fix: allow to omit region name in endregion tag in code snippets

* fix: allow leading spaces in code block

* Discard changes to packages/slidev/node/syntax/transform/snippet.ts

* allow tab

Author: kermanx

packages/slidev/node/syntax/transform/code-wrapper.ts

@@ -2,7 +2,7 @@ import type { MarkdownTransformContext } from '@slidev/types'
 import { normalizeRangeStr } from './utils'
 
 // eslint-disable-next-line regexp/no-super-linear-backtracking
-export const reCodeBlock = /^```([\w'-]+)?\s*(?:\{([\w*,|-]+)\}\s*?(\{[^}]*\})?([^\r\n]*))?\r?\n(\S[\s\S]*?)^```$/gm
+export const reCodeBlock = /^```([\w'-]+)?\s*(?:\{([\w*,|-]+)\}\s*?(\{[^}]*\})?([^\r\n]*))?\r?\n([ \t]*\S[\s\S]*?)^```$/gm
 
 /**
  * Transform code block with wrapper