fix: Improve README and drop quotes from hook env vars (#651)

README.md

@@ -322,14 +322,18 @@ If for config above set up `export CONFIG_NAME=.tflint; export CONFIG_EXT=hcl` b
 
 You can specify environment variables that will be passed to the hook at runtime.
 
+> [!IMPORTANT]
+> Variable values are exported _verbatim_:
+> - No interpolation or expansion are applied
+> - The enclosing double quotes are removed if they are provided
+
 Config example:
 
 ```yaml
 - id: terraform_validate
   args:
     - --env-vars=AWS_DEFAULT_REGION="us-west-2"
-    - --env-vars=AWS_ACCESS_KEY_ID="anaccesskey"
-    - --env-vars=AWS_SECRET_ACCESS_KEY="asecretkey"
+    - --env-vars=AWS_PROFILE="my-aws-cli-profile"
 ```
 
 ### All hooks: Disable color output

hooks/_common.sh

@@ -527,6 +527,11 @@ function common::export_provided_env_vars {
   for var in "${env_vars[@]}"; do
     var_name="${var%%=*}"
     var_value="${var#*=}"
+    # Drop enclosing double quotes
+    if [[ $var_value =~ ^\" && $var_value =~ \"$ ]]; then
+      var_value="${var_value#\"}"
+      var_value="${var_value%\"}"
+    fi
     # shellcheck disable=SC2086
     export $var_name="$var_value"
   done