Move CLLE.xshd and RPGLE.xshd to /ThirdParty-Highlightings/ as we are not planning on shipping every possible highlighting definition with AvalonEdit.

ThirdParty-Highlightings/README.md

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+Third-Party Highlighting Definitions for AvalonEdit
+==================================================
+
+These custom highlighting definitions have been provided by the community.
+We are sharing them here, because we cannot include every possible language in the AvalonEdit bundle.
+
+If you want your highlighting included, please open a pull request.
+
+* [RPG](https://www.ibm.com/support/knowledgecenter/ssw_ibm_i_73/rbam6/rbam6clmain.htm) see RPGLE.xshd
+* [CLLE](https://www.ibm.com/developerworks/ibmi/library/i-ibmi-rpg-support/index.html) see CLLE.xshd
+
+Highlighting Definitions found in other locations
+------------------------------------------------
+
+* Assembler highlighting (shipping with ILSpy): https://github.com/icsharpcode/ILSpy/blob/master/ILSpy/TextView/Asm-Mode.xshd
+* MSIL highlighting (shipping with ILSpy): https://github.com/icsharpcode/ILSpy/blob/master/ILSpy/TextView/ILAsm-Mode.xshd