Remove some categories in favor of single page enties.

website/docs/cmixx/design-specs/_category_.json

website/docs/dapps/intro.md

website/docs/dapps/phoenixx.md

website/docs/dapps/speakeasy.md

website/docs/intro.md

website/docs/overview/cmixx.md

website/docs/overview/softwareOverview.md

website/docs/overview/xxchain.md

website/docs/overview/xxnetwork.md

website/docs/tools/dashboard.md

website/docs/tools/explorer.md

website/docs/tools/explorer/_category_.json

website/docs/tools/simpleStaking.md

website/docs/tools/simpleStaking/_category_.json

website/docs/tools/simpleStaking/simpleStaking.md

website/docs/tools/sleeve.md

website/docs/tools/sleeve/_category_.json

website/docs/tools/webWallet/accounts/accountTypes.md

website/docs/tools/webWallet/accounts/addContact.md

website/docs/tools/webWallet/governance/voting.md