Expose docker socket to container

See #1257, release log:

• b06b2bd by @yegor256: #1257 share docker socket
• 73c364f by @yegor256: #1256 better message
• 7f80d49 by @yegor256: simplified
• 7f20a95 by @yegor256: donate badge
• cc054bb by @yegor256: #1252 jcabi-github 0.34

Released by Rultor 1.67.3, see build log