Fix formatting of gethash examples

[fosskers]

I'm on a work computer where the node version is way too old, so I was unable to test this myself, but either way the current rendering online is quite strange, and this PR is an attempt to fix that:

https://lisp-docs.github.io/cl-language-reference/chap-18/bi-c-dictionary/gethash_accessor

Overall the syntax examples on these pages could perhaps be improve en masse by using code fences.

[daninus14]

Thanks for the help! Yeah, there are a bunch of missing code blocks we have to add and a lot of tables need to be formatted to display the information correctly. I've been busy with some other projects, but I do hope to be able to get back to this.

I'm planning on switching from node to a CL based rendering (which I have to make) and change the way the files are named to make it easier for people to contribute. Because of using mdx, which is a react renderer used by Docusaurus, I had to rename all files to not include numbers in their names, which confuses people.

Anyways, thanks so much for your contributions! They are appreciated. I hopefully will get back to changing the engine of the whole project to CL to make it easier to contribute, but that includes making indices for search and a few other details which will probably take me a couple of weekends at least, time which I don't have available right now.

[daninus14]

Your changes are now live! 😄