As mentioned here also, plain {% raw %} and {% endraw %} are only the second best solution since those are shown if you look up the Markdown on normal github.com.
The best way is to put {% raw %} and {% endraw %} in HTML comments:
<!-- {% raw %} -->
something with curlky brackets like { this } and { that }
<!-- {% endraw %} -->
Due to the HTML comments it is seen by Github as a comment. In Github pages the raw tags will prevent the parsing of the curly brackets in between the tags.