If you summarize your idea in your first sentence, writing "TLDR" is superfluous.
The English Language already has tools to summarize and communicate your thoughts. Leverage existing conventions, which are accepted by a larger population, and you will engage more users and succeed in communicating your idea.
"TLDR" stands for "Too Long, didn't read", and began as a response to the "wall of text" style of writing that would appear on sites like Reddit. Over time, it became a shorthand way of saying "Here's a summary.". However, if you actually wrote the article, it is asinine to preface it with "Too Long; Didn't Read". Of course you read it. You wrote it.Instead, edit your article, and make sure to summarize your point in the first sentence.