feat(core): allow custom filter per source

fixes #13

lua/care/core.lua

@@ -15,6 +15,7 @@ end
 function core:complete(reason)
     reason = reason or 2
     local sources = require("care.sources").get_sources()
+    ---@type care.entry[]
     local entries = {}
     local remaining = #sources
     self.context.reason = reason
@@ -35,6 +36,9 @@ function core:complete(reason)
                     local filtered_items = vim.iter(items):filter(function(entry)
                         return not entry.score or entry.score > 0
                     end)
+                    if source.config.filter then
+                        filtered_items:filter(source.config.filter)
+                    end
                     if source.config.max_entries then
                         filtered_items:take(source.config.max_entries)
                     end

lua/care/types/config.lua

@@ -51,6 +51,8 @@
 ---@field max_entries integer?
 --- The priority of this source. Is more important than matching score
 ---@field priority integer?
+--- Filter function for entries by the source
+---@field filter fun(entry: care.entry): boolean
 
 --- Configuration of the completion menu of care.nvim
 ---@class care.config.ui.docs