lime-webui add dependency from luci-compat

[ilario]

lime-webui is obsolete and has been replaced by lime-app since years.
Anyway, there are still users using it.

Since OpenWrt 19.07, some LuCI pieces have been moved to the luci-compat package and adding it as a dependency should not be a problem neither for people still using OpenWrt 18.06 as a base as an empty package with this name has been added in its repositories.

If this package is not selected, the shown error is the following:

/usr/lib/lua/luci/dispatcher.lua:1334: module 'luci.cbi' not found:
	no field package.preload['luci.cbi']
	no file './luci/cbi.lua'
	no file '/usr/share/lua/luci/cbi.lua'
	no file '/usr/share/lua/luci/cbi/init.lua'
	no file '/usr/lib/lua/luci/cbi.lua'
	no file '/usr/lib/lua/luci/cbi/init.lua'
	no file './luci/cbi.so'
	no file '/usr/lib/lua/luci/cbi.so'
	no file '/usr/lib/lua/loadall.so'
	no file './luci.so'
	no file '/usr/lib/lua/luci.so'
	no file '/usr/lib/lua/loadall.so'
stack traceback:
	[C]: in function 'require'
	/usr/lib/lua/luci/dispatcher.lua:1334: in function '_cbi'
	/usr/lib/lua/luci/dispatcher.lua:1023: in function 'dispatch'
	/usr/lib/lua/luci/dispatcher.lua:984: in function 'dispatch'
	/usr/lib/lua/luci/dispatcher.lua:478: in function </usr/lib/lua/luci/dispatcher.lua:477>

[codecov-commenter]

Codecov Report

Merging #899 (947f226) into master (58bb697) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #899   +/-   ##
=======================================
  Coverage   74.54%   74.54%           
=======================================
  Files          43       43           
  Lines        3658     3658           
=======================================
  Hits         2727     2727           
  Misses        931      931           

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