findBestMatch should be case insensitive

[ramya-rao-a]

@sergeche According to the current css-snippets-resolver,

trf:r best matches with transform: rotate(${1:angle}

trf:rX best matches with transform: rotateX(${1:angle}

but

trf:rx best matches with transform: rotate(${1:angle} instead of transform: rotateX(${1:angle}