update urfave/cli v1.22.1, go-md2man v2.0.0, blackfriday v2.0.1

This updates urfave/cli and its dependencies to v1.22.1:

- diff for urfave/cli: https://github.com/urfave/cli/compare/v1.22.0...v1.22.1
- diff for go-md2man: https://github.com/cpuguy83/go-md2man/compare/v1.0.10...v2.0.0
- diff for blackfriday: https://github.com/russross/blackfriday/compare/v1.5.2...v2.0.1

Also adds github.com/shurcooL/sanitized_anchor_name as a new dependency, which is
used by russross/blackfriday, but will be removed again in a future update (dependency
is already removed on the v2 branch through russross/blackfriday@919b1f5b9b

Signed-off-by: Sebastiaan van Stijn <github@gone.nl>

.github/workflows/ci.yml

@@ -199,7 +199,7 @@ jobs:
           path: src/github.com/containerd/containerd
 
       - name: Install dependencies
-        run: go get -u github.com/cpuguy83/go-md2man
+        run: GO111MODULE=on go get github.com/cpuguy83/go-md2man/v2@v2.0.0
 
       - name: Make
         run: make man