public Builder putCaseInsensitive(String reservedWord, String conversion) {
            caseInsensitiveMappings.put(reservedWord.toLowerCase(Locale.US), conversion);
            return this;
        }
Add a new case-insensitive reserved word that converts the given
reserved word to the given conversion string.

<p>Note that the conversion string is used literally. The casing
of the original word has no effect on the conversion. Use
{@link ReservedWordsBuilder} for a case-insensitive reserved words
implementation that can take casing into account.

@param reservedWord Case-insensitive reserved word to convert.
@param conversion Word to convert to.
@return Returns the builder.
smithy-codegen-core/src/main/java/software/amazon/smithy/codegen/core/MappedReservedWords.java