ci: Tweak command parsing

 - Fix wrong index variable in loop ("i" vs "INDEX") that prevented
   detection of commands at arbitrary places in a comment.
 - Normalize commands to lowercase before checking them.
 - Allow the user to say "please" because it just feels nicer to me,
   even when I'm talking to a robot.

.github/workflows/shaka-bot-commands/lib.sh

@@ -64,17 +64,30 @@ function start_workflow() {
   gh workflow run "$WORKFLOW" -R "$THIS_REPO" "${GH_ARGS[@]}"
 }
 
+# Simple alias for converting a stream of text to lowercase.
+function tolower() {
+  tr '[:upper:]' '[:lower:]'
+}
+
 # Outputs to global variables SHAKA_BOT_COMMAND and SHAKA_BOT_ARGUMENTS (array).
 function parse_command() {
   # Tokenize the comment by whitespace.
   local TOKENS=( $COMMENT_BODY )
 
   local INDEX
   for (( INDEX=0; INDEX < ${#TOKENS[@]}; INDEX++ )); do
-    if [[ "${TOKENS[i]}" == "@shaka-bot" ]]; then
-      SHAKA_BOT_COMMAND="${TOKENS[i+1]}"
-      # A slice of all tokens starting with index i+2.
-      SHAKA_BOT_ARGUMENTS=( "${TOKENS[@]:i+2}" )
+    if [[ "${TOKENS[INDEX]}" == "@shaka-bot" ]]; then
+      # The next word is the command.
+      SHAKA_BOT_COMMAND=$(echo "${TOKENS[INDEX+1]}" | tolower)
+
+      # Unless it's please, then it's the word after that.
+      if [[ "$SHAKA_BOT_COMMAND" == "please" ]]; then
+        INDEX=$((INDEX + 1))
+        SHAKA_BOT_COMMAND=$(echo "${TOKENS[INDEX+1]}" | tolower)
+      fi
+
+      # A slice of all tokens starting with index INDEX+2.
+      SHAKA_BOT_ARGUMENTS=( "${TOKENS[@]:INDEX+2}" )
       return 0
     fi
   done