Contiguous Token are Wrapped in Single <span>

During tests, I've noticed that contiguous same-tokens are highlighted using a single <span>, which doesn't create problems when using Highlight themes, but can be a problem when using custom CSS.

For example, in the EXAPUNKS test syntax_test_registers.exa:

COPY X T
;    ^ kwb
;      ^ kwb

the HTML output is:

<span class="hl kwb">X T</span>

In the actual tests, which use a custom CSS theme with bacgkround colors for keywords, these two elements look like one element.

Ideally, Highlight should keep each element individually wrapped in its own <span>. Although this would produce a more verbose output, it would be a more correct representation of the code.

My guess is that other users rely on custom CSS too, and some syntaxes demand background coloring of some elements (e.g. diffs, but also markup syntaxes).