Fix Look & Feel for the Testcontainers for C/C++ website

[oleg-nenashev]

Currently, we moved the site to https://testcontainers.github.io/testcontainers-native/ , but its look & feel is different from other Testcontainers site

Quick wins

• Fix logos in the dark mode

Bigger stories

• Apply branding of Testcontainers, similar to other project sites. The styling from https://node.testcontainers.org/ can be used
• Update headers and footers to follow the style

Everything can be done via incremental PRs