Please document the role of Active profile in Eclipse configuration

The README states: “The plugin adds a google-java-format formatter implementation that can be configured in Window > Preferences > Java > Code Style > Formatter > Formatter Implementation.”

It is unclear what can be configured exactly, or whether anything can be configured, considering the note in the same file: “There is no configurability as to the formatter's algorithm for formatting. This is a deliberate design decision to unify our code formatting on a single format.”

Relatedly, the role of the Active profile dialog box is not clear.

I just tested changing the number of spaces in the active profile, and this seems to have no effect on Source / Format when the google-java-format implementation is selected.

Please add some explanations about what can be configured and which Active profile should be chosen or indicate if it is supposed to have no effect.

從 README.md 的 Eclipse 部分開始，使用 Eclipse 的 Active profile 設定並選取 google-java-format 實作來重現回報的行為。記錄 formatter 設定和 Active profile 控制的內容，包括 profile 變更是否會影響 Source / Format，讓 README 清楚說明應選取哪個 profile。