Add Justfile with tasks for testing plugin locally in isolation of user settings

Author: alerque

Justfile

@@ -0,0 +1,25 @@
+set ignore-comments := true
+set unstable := true
+
+just := just_executable()
+vim := which('vim')
+nvim := which('nvim')
+
+[default]
+[private]
+@help:
+    {{ just }} --list --unsorted
+
+[no-cd]
+preview-vim *ARGS: (preview vim + ' -N -u NORC -i NONE -c "filetype plugin on | syntax on"' ARGS)
+
+[no-cd]
+preview-nvim *ARGS: (preview nvim + ' --clean' ARGS)
+
+[no-cd]
+[private]
+preview vimcmd *ARGS:
+    {{ vimcmd }} \
+    	-c {{ quote("let &runtimepath=\"" + justfile_directory() + ",\" . &runtimepath") }} \
+    	-c 'filetype detect' \
+    	{{ ARGS }}