docs: add usage and examples for sshrm

README.md

@@ -1,2 +1,34 @@
 # sshrm
 
+Remove an entry from `~/.ssh/known_hosts` by host name or by line number.
+
+## Usage
+
+```bash
+sshrm [OPTION]... HOST|LINE
+```
+
+## Options
+
+- `-h`, `--help` Show help and exit.
+
+## Examples
+
+Remove by host:
+
+```bash
+sshrm example.com
+```
+
+Remove by line number:
+
+```bash
+sshrm 12
+```
+
+## Notes
+
+- Line numbers must be positive integers.
+- The script edits `~/.ssh/known_hosts`.
+- Keep a backup if you need to recover entries.
+