refactor: revert remove dead context.get_keyword

Closes #891

6df3f68 'refactor: remove dead `context.get_keyword`'

lua/blink/cmp/completion/trigger/context.lua

@@ -17,6 +17,7 @@
 --- @field providers string[]
 ---
 --- @field new fun(opts: blink.cmp.ContextOpts): blink.cmp.Context
+--- @field get_keyword fun(): string
 --- @field within_query_bounds fun(self: blink.cmp.Context, cursor: number[]): boolean
 ---
 --- @field get_mode fun(): blink.cmp.Mode
@@ -64,6 +65,12 @@ function context.new(opts)
   }, { __index = context })
 end
 
+function context.get_keyword()
+  local keyword = require('blink.cmp.config').completion.keyword
+  local range = context.get_bounds(keyword.range)
+  return string.sub(context.get_line(), range.start_col, range.start_col + range.length - 1)
+end
+
 --- @param cursor number[]
 --- @return boolean
 function context:within_query_bounds(cursor)