sample/src/main/java/ru/noties/markwon/sample/customextension/IconProcessor.java
@NonNull
    public static String prepare(@NonNull String input) {
        final StringBuilder builder = new StringBuilder(input);
        prepare(builder);
        return builder.toString();
    }
@NonNull
    public static String prepare(@NonNull String input) {
        final StringBuilder builder = new StringBuilder(input);
        prepare(builder);
        return builder.toString();
    }
Should be used when input string does not wrap icon definition with `@` from both ends.
So, `@ic-home-white-24` would become `@ic-home-white-24@`. This way parsing is easier
and more predictable (cannot specify multiple ending delimiters, as we would require them:
space, newline, end of a document, and a lot of more)

@param input to process
@return processed string
@see #prepare(StringBuilder)