We’ve developed a plugin for IntelliJ Platform which uses LanguageTool as a proofreader.
It is called Grazi and can be found in official jetbrains plugins repository (here)
There are a lot of things to do, but it will be extremely helpful if you will try and let us know with any bugs, issues or subjects to enhance.
Right now it supports few markup languages (XML, Markdown), comments in any language and plain text. Also, we have extended support of Java, Kotlin and Python. It means that docs and literal strings (including formatted) are also checked.
Plugin is open source, code and issues are on GitHub (here)