refactor: Lua 模块化

删除 `rime.lua`，拆分到 `lua/` 文件夹内。
方案中的 `- lua_xxx@xxx` 修改为 `- lua_xxx@*xxx`（加一个星号）。

lua/select_character.lua

@@ -0,0 +1,83 @@
+-- 以词定字
+-- 来源 https://github.com/BlindingDark/rime-lua-select-character
+-- 删除了默认按键 [ ]，和方括号翻页冲突，需要在 key_binder 下指定才能生效
+local function utf8_sub(s, i, j)
+    i = i or 1
+    j = j or -1
+
+    if i < 1 or j < 1 then
+        local n = utf8.len(s)
+        if not n then
+            return nil
+        end
+        if i < 0 then
+            i = n + 1 + i
+        end
+        if j < 0 then
+            j = n + 1 + j
+        end
+        if i < 0 then
+            i = 1
+        elseif i > n then
+            i = n
+        end
+        if j < 0 then
+            j = 1
+        elseif j > n then
+            j = n
+        end
+    end
+
+    if j < i then
+        return ""
+    end
+
+    i = utf8.offset(s, i)
+    j = utf8.offset(s, j + 1)
+
+    if i and j then
+        return s:sub(i, j - 1)
+    elseif i then
+        return s:sub(i)
+    else
+        return ""
+    end
+end
+
+local function first_character(s)
+    return utf8_sub(s, 1, 1)
+end
+
+local function last_character(s)
+    return utf8_sub(s, -1, -1)
+end
+
+local function select_character(key, env)
+    local engine = env.engine
+    local context = engine.context
+    local commit_text = context:get_commit_text()
+    local config = engine.schema.config
+
+    -- local first_key = config:get_string('key_binder/select_first_character') or 'bracketleft'
+    -- local last_key = config:get_string('key_binder/select_last_character') or 'bracketright'
+    local first_key = config:get_string('key_binder/select_first_character')
+    local last_key = config:get_string('key_binder/select_last_character')
+
+    if (key:repr() == first_key and commit_text ~= "") then
+        engine:commit_text(first_character(commit_text))
+        context:clear()
+
+        return 1 -- kAccepted
+    end
+
+    if (key:repr() == last_key and commit_text ~= "") then
+        engine:commit_text(last_character(commit_text))
+        context:clear()
+
+        return 1 -- kAccepted
+    end
+
+    return 2 -- kNoop
+end
+
+return select_character