DOC: Format remote module documentation README to markdown.

Modules/Remote/README.md

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+Introduction
+============
+
+This directory is a place-holder for all remote modules distributed outside
+ITK's main repository. Remote modules share the same directory structure as
+modules in the main repository. They will be picked up by the configuration
+system and entered into the build after they are downloaded into this
+directory.
+
+Modules can easily be downloaded and made accessible to the community by
+listing the module in the current directory. For more information on the
+policy and procedures for adding a new module, please visit the
+[Contributing with a Remote Module](https://itk.org/ITKSoftwareGuide/html/Book1/ITKSoftwareGuide-Book1ch9.html#x55-1640009.7)  in the [ITK Software Guide].
+
+For more information on adding a new module to the list of new modules,
+please visit the [ITKModuleTemplate](https://github.com/InsightSoftwareConsortium/ITKModuleTemplate) repository.
+
+Note that in each `<remote module name>.remote.cmake` file, the first argument
+of the function `itk_fetch_module()` is the name of the remote module, and it
+has to be consistent with the module name defined in the correponding
+`<remote module name>.remote.cmake` file.
+
+To better distinguish the remote modules from the internal ITK modules, the names
+of the remote modules should **not** contain the "ITK" string prefix in them.
+
+
+[ITK Software Guide]: https://itk.org/ItkSoftwareGuide.pdf