Fix README to specify Zola 0.18

[BD103]

Unfortunately I didn't have time to catch #1600 before it was merged. The website actually uses Zola 0.18, not 0.17.2! It was updated last February in #1018.

Note how we pull in shalzz/[email protected]:

bevy-website/.github/workflows/ci.yml

Lines 247 to 253 in e285dfd

	- name: "Build website"
	uses: shalzz/[email protected]
	env:
	PAGES_BRANCH: gh-pages
	BUILD_DIR: .
	BUILD_ONLY: true
	TOKEN: fake-secret

bevy-website/.github/workflows/deploy.yml

Lines 47 to 53 in e285dfd

	- name: "Build and deploy website"
	if: github.repository_owner == 'bevyengine'
	uses: shalzz/[email protected]
	env:
	PAGES_BRANCH: gh-pages
	BUILD_DIR: .
	TOKEN: ${{ secrets.CART_PAT }}

[victorb]

Ah, my bad, based it solely on a Discord comment from @alice-i-cecile (just to wash my hands clear 🤣 )

[alice-i-cecile]

Yeah, that was just based on me checking what version I was running locally (which worked!). Definitely my fault!

[BD103]

No worries, just trying to clear the confusion!