adding github action for checking broken links

[RinkiyaKeDad]

Signed-off-by: Arsh Sharma arshsharma461@gmail.com

Uses: https://github.com/gaurav-nelson/github-action-markdown-link-check

[RinkiyaKeDad]

Example of failed output:

=========================> MARKDOWN LINK CHECK <=========================

FILE: ./helm/README.md

2 links checked.

FILE: ./php/README.md

7 links checked.

FILE: ./rails/README.md
[✖] https://github.com/okteto/okteto/blob/master/docs/installation.md → Status: [40](https://github.com/okteto/samples/runs/5625717478?check_suite_focus=true#step:4:40)4

6 links checked.

ERROR: 1 dead links found!
[✖] https://github.com/okteto/okteto/blob/master/docs/installation.md → Status: 404

FILE: ./jib/README.md

5 links checked.

FILE: ./coder/README.md

3 links checked.

FILE: ./README.md

[59](https://github.com/okteto/samples/runs/5625717478?check_suite_focus=true#step:4:59) links checked.

=========================================================================

[RinkiyaKeDad]

I'm letting the broken link in the rails README remain until we merge this PR so everyone can see the output of the action.