replace rice file embedding with native embedding of go1.16

go.mod

go.sum

internal/server/middlerwares.go

internal/server/server.go

internal/server/web/layouts/main.mustache

internal/server/web/partials/error-message.mustache

internal/server/web/partials/footer.mustache

internal/server/web/partials/mytokens.mustache

internal/server/web/partials/navbar.mustache

internal/server/web/partials/scripts.mustache

internal/server/web/partials/style.mustache

internal/server/web/sites/404.mustache

internal/server/web/sites/405.mustache

internal/server/web/sites/429.mustache

internal/server/web/sites/500.mustache

internal/server/web/sites/501.mustache

internal/server/web/sites/505.mustache

internal/server/web/sites/consent.mustache

internal/server/web/sites/home.mustache

internal/server/web/sites/index.mustache