docs: add comment block to package slackcontext (#62)

* docs: add comment block to package slackcontext

* Update internal/slackcontext/slackcontext.go

Co-authored-by: Eden Zimbelman <eden.zimbelman@salesforce.com>

* docs: tweak wording from request-scope to execution-scope

---------

Co-authored-by: Eden Zimbelman <eden.zimbelman@salesforce.com>

Author: mwbrooks

internal/slackcontext/slackcontext.go

@@ -12,6 +12,18 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
+// Package slackcontext defines getters and setters for execution-scoped values
+// that are propagated through context.Context during the execution of a Slack
+// command. These values may include unique identifiers, session metadata, host
+// information, version details, and other execution data.
+//
+// All values should be set in the context before a Slack command begins execution.
+// The values can then be accessed throughout the command's execution lifecycle
+// using the provided getter methods.
+//
+// Each value is stored with an unexported key type to prevent collisions with
+// other packages using context values. The package provides type-safe accessors
+// for retrieving these values.
 package slackcontext
 
 import (