Add description for auto correction threshold strings

    <string name="auto_correction_summary">Spacebar and punctuation automatically insert highlighted word</string>

    <!-- Option to disable auto correction. [CHAR LIMIT=20] -->

    <string name="auto_correction_threshold_mode_off">Off</string>

    <!-- Option to use modest auto correction. [CHAR LIMIT=20] -->

    <!-- Option to suggest auto correction candidates modestly. Auto-corrects only to a word which has small edit distance from typed word. [CHAR LIMIT=20] -->

    <string name="auto_correction_threshold_mode_modest">Modest</string>

    <!-- Option to use aggressive auto correction. [CHAR LIMIT=20] -->

    <!-- Option to suggest auto correction candidates aggressively. Auto-corrects to a word which has even large edit distance from typed word. [CHAR LIMIT=20] -->

    <string name="auto_correction_threshold_mode_aggeressive">Aggressive</string>

    <!-- Option to enable bigram correction -->