runtime(idris2): include filetype,indent+syntax plugins for (L)Idris2 + ipkg

closes: #15993

Co-authored-by: Christian Clason <ch.clason+github@icloud.com>
Signed-off-by: Serhii Khoma <srghma@gmail.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>

runtime/syntax/lidris2.vim

@@ -0,0 +1,25 @@
+" Vim syntax file
+" Language:    Literate Idris 2
+" Maintainer:  Idris Hackers (https://github.com/edwinb/idris2-vim), Serhii Khoma <srghma@gmail.com>
+" Last Change: 2020 May 19
+" Version:     0.1
+" License:     Vim (see :h license)
+" Repository:  https://github.com/ShinKage/idris2-nvim
+"
+" This is just a minimal adaption of the Literate Haskell syntax file.
+
+" quit when a syntax file was already loaded
+if exists("b:current_syntax")
+  finish
+endif
+
+" Read Idris highlighting.
+syntax include @idris2Top syntax/idris2.vim
+
+" Recognize blocks of Bird tracks, highlight as Idris.
+syntax region lidris2BirdTrackBlock start="^>" end="\%(^[^>]\)\@=" contains=@idris2Top,lidris2BirdTrack
+syntax match  lidris2BirdTrack "^>" contained
+
+hi def link   lidris2BirdTrack Comment
+
+let b:current_syntax = "lidris2"