docs: fisher and plugins are automatically installed

- A bootstrap script in the config.fish file handles automatic
installation of fisher and the included plugins upon launching the shell
for the first time

README.md

@@ -79,11 +79,7 @@ Managed via [Fisher](https://github.com/jorgebucaran/fisher):
 | `mattmc3/magic-enter.fish` | Smart Enter: runs `ls` / `git status` on blank line |
 | `jorgebucaran/spark.fish` | Sparkline bar charts in the terminal |
 
-Install plugins after cloning:
-
-```fish
-fisher update
-```
+Fisher and all listed plugins are installed automatically by the bootstrap script in `config.fish` upon launching the shell for the first time.
 
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