docs: add note to froyo platform doc that not all locales are included in the sdk image

<p>Localized UI strings match the locales that are accessible

through Settings.</p>

<p class="note"><strong>Note:</strong> Android supports more locales than are listed above. However,

the entire collection of locale strings cannot fit on a single system image, so the above list is

only what's included in the system image for the SDK. All of Android's supported locales are

available in the <a href="http://source.android.com/">Android Open Source Project</a>.</p>

<h2 id="skins">Emulator Skins</h2>

<p>The downloadable platform includes a set of emulator skins that you can use