Add host to etcd cluster

[enggnr]

• What kind of change does this PR introduce? (Bug fix, feature, docs update, ...) Provides a script to add the host to etcd cluster

• What is the new behavior (if this is a feature change)? Fixes #29

@ProfessorManhattan, please note that the IP addresses that etcd advertises/listens to are taken from hostname command. In cases where there may be multiple IPs assigned to the host, and a specific IP is to be used for etcd, then that can be made an input. Please share your thoughts on this.

[github-actions[bot]]

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Files not summarized due to errors (2)

### Failed to summarize * home/.chezmoi.yaml.tmpl (nothing obtained from openai) * home/.chezmoiscripts/universal/run_onchange_before_11-join-etcd-cluster.tmpl (nothing obtained from openai)

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In the recent run, only the files that changed from the base of the PR and between d6e9d2d434f14f429d4b15af9ce23e236f69d1e6 and fa3b21e55b28b39719aaef472ed50c33228b1640 commits were reviewed.

Files not reviewed due to errors in the recent run (2)

### Failed to review in the last run * home/.chezmoiscripts/universal/run_onchange_before_11-join-etcd-cluster.tmpl (no response) * home/.chezmoi.yaml.tmpl (no response)

[ProfessorManhattan]

Hey @enggnr --- left a few comments on other threads --- please let me know if you have any ideas on how to set up network discovery / auto-joining for these various services.