Document how imports work

As noted in https://github.com/bytecodealliance/ComponentizeJS/issues/88, it is not obvious how imports work. While I understand the hesitation to document this extensively as things are likely to change in the future, it makes it very hard for new comers to ComponentizeJS to use the tool if there is absolutely no documentation about how to call imports.

首先查看 issue #88 以及 ComponentizeJS 目前的 import 行為。透過一個具體的使用範例，記錄使用者如何呼叫 imports；當新貢獻者不需要未記錄的上下文即可遵循文件中的流程時，這項工作就完成了。

由索引模型根據 Issue 內容生成。