Bump Nim in the ARM64 Dockerfile, add nitter user

Dockerfile.arm64

@@ -1,7 +1,7 @@
 FROM alpine:3.18 as nim
 LABEL maintainer="[email protected]"
 
-RUN apk --no-cache add gcc git libc-dev libsass-dev "nim=1.6.14-r0" nimble pcre
+RUN apk --no-cache add libsass-dev pcre gcc git libc-dev "nim=1.6.16-r0" "nimble=0.13.1-r3"
 
 WORKDIR /src/nitter
 
@@ -15,9 +15,11 @@ RUN nimble build -d:danger -d:lto -d:strip \
 
 FROM alpine:3.18
 WORKDIR /src/
-RUN apk --no-cache add ca-certificates pcre openssl1.1-compat
+RUN apk --no-cache add pcre ca-certificates openssl1.1-compat
 COPY --from=nim /src/nitter/nitter ./
 COPY --from=nim /src/nitter/nitter.example.conf ./nitter.conf
 COPY --from=nim /src/nitter/public ./public
 EXPOSE 8080
+RUN adduser -h /src/ -D -s /bin/sh nitter
+USER nitter
 CMD ./nitter