runtime(tsx): add indentation plugin (fixes #13574) (#13576)

for now, let's just use the typescript indent file.

Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/runtime/indent/typescriptreact.vim b/runtime/indent/typescriptreact.vim
new file mode 100644
index 0000000..052bddd
--- /dev/null
+++ b/runtime/indent/typescriptreact.vim
@@ -0,0 +1,2 @@
+" Placeholder for backwards compatilibity: .tsx used to stand for TypeScript.
+runtime! indent/typescript.vim