Fix broken image path in CONTRIBUTING and malformed link in Niksa.md - #20460

Failed to retrieve cspell:cpp/src/stdlib-c.txt -- HTTP 404 for https://raw.githubusercontent.com/check-spelling/cspell-dicts/v20241114/dictionaries/cpp/src/stdlib-c.txt (check-dictionary-not-found)

Failed to retrieve cspell:cpp/src/people.txt -- HTTP 404 for https://raw.githubusercontent.com/check-spelling/cspell-dicts/v20241114/dictionaries/cpp/src/people.txt (check-dictionary-not-found)

Failed to retrieve cspell:cpp/src/lang-keywords.txt -- HTTP 404 for https://raw.githubusercontent.com/check-spelling/cspell-dicts/v20241114/dictionaries/cpp/src/lang-keywords.txt (check-dictionary-not-found)

Failed to retrieve cspell:cpp/src/lang-jargon.txt -- HTTP 404 for https://raw.githubusercontent.com/check-spelling/cspell-dicts/v20241114/dictionaries/cpp/src/lang-jargon.txt (check-dictionary-not-found)

Failed to retrieve cspell:cpp/src/ecosystem.txt -- HTTP 404 for https://raw.githubusercontent.com/check-spelling/cspell-dicts/v20241114/dictionaries/cpp/src/ecosystem.txt (check-dictionary-not-found)

Failed to retrieve cspell:cpp/src/compiler-msvc.txt -- HTTP 404 for https://raw.githubusercontent.com/check-spelling/cspell-dicts/v20241114/dictionaries/cpp/src/compiler-msvc.txt (check-dictionary-not-found)

Failed to retrieve cspell:cpp/src/compiler-gcc.txt -- HTTP 404 for https://raw.githubusercontent.com/check-spelling/cspell-dicts/v20241114/dictionaries/cpp/src/compiler-gcc.txt (check-dictionary-not-found)

Failed to retrieve cspell:cpp/src/compiler-clang-attributes.txt -- HTTP 404 for https://raw.githubusercontent.com/check-spelling/cspell-dicts/v20241114/dictionaries/cpp/src/compiler-clang-attributes.txt (check-dictionary-not-found)

Failed to retrieve cspell:clojure/src/clojure.txt -- HTTP 404 for https://raw.githubusercontent.com/check-spelling/cspell-dicts/v20241114/dictionaries/clojure/src/clojure.txt (check-dictionary-not-found)