chore: rename the project to ghglance

The Marketplace rejects ghstats as an action name, so the repo, Go module,
binary, and action share the name ghglance instead. The demo workflow keeps
reading the existing GHSTATS_TOKEN repo secret.

Dockerfile

@@ -3,11 +3,11 @@ WORKDIR /src
 COPY go.mod ./
 RUN go mod download || true
 COPY . .
-RUN CGO_ENABLED=0 go build -trimpath -ldflags="-s -w" -o /out/ghstats .
+RUN CGO_ENABLED=0 go build -trimpath -ldflags="-s -w" -o /out/ghglance .
 
 FROM alpine:3.21@sha256:48b0309ca019d89d40f670aa1bc06e426dc0931948452e8491e3d65087abc07d
 RUN apk add --no-cache ca-certificates tzdata git
-COPY --from=build /out/ghstats /usr/local/bin/ghstats
+COPY --from=build /out/ghglance /usr/local/bin/ghglance
 COPY entrypoint.sh /entrypoint.sh
 RUN chmod +x /entrypoint.sh
 ENTRYPOINT ["/entrypoint.sh"]