chore: update readme to include new subcommand

Author: Erin van der Veen

README.md

@@ -184,6 +184,7 @@ Commands:
   format      Format inputs
   visualise   Visualise the input's Tree-sitter parse tree
   config      Print the current configuration
+  prefetch    Prefetch all languages in the configuration
   completion  Generate shell completion script
   help        Print this message or the help of the given subcommand(s)
 
@@ -345,6 +346,26 @@ For example, in Bash:
 source <(topiary completion)
 ```
 
+#### Prefetching
+
+Topiary dynamically downloads, builds, and loads the tree-sitter grammars. In
+order to ensure offline availability or speed up startup time, the grammars can
+be prefetched and compiled.
+
+<!-- DO NOT REMOVE THE "usage" COMMENTS -->
+<!-- usage:start:prefetch-->
+```
+Prefetch all languages in the configuration
+
+Usage: topiary prefetch [OPTIONS]
+
+Options:
+  -C, --configuration <CONFIGURATION>  Configuration file [env: TOPIARY_CONFIG_FILE]
+  -v, --verbose...                     Logging verbosity (increased per occurrence)
+  -h, --help                           Print help
+```
+<!-- usage:end:prefetch -->
+
 #### Logging
 
 By default, the Topiary CLI will only output error messages. You can

bin/verify-documented-usage.sh

@@ -40,7 +40,7 @@ diff-usage() {
 }
 
 main() {
-  local -a subcommands=(ROOT format visualise config completion)
+  local -a subcommands=(ROOT format visualise config completion prefetch)
 
   local _diff
   local _subcommand