Move build files to 'firefox' folder

In preparation for merging the support for Chrome impersonation, move
all build files to the 'firefox' folder. The two builds will live
separately as they are rather different (using two different SSL
libraries for instance).

firefox/Dockerfile

@@ -33,7 +33,7 @@ RUN curl -o ${NGHTTP2_VERSION}.tar.bz2 -L ${NGHTTP2_URL}
 RUN tar xf ${NGHTTP2_VERSION}.tar.bz2
 
 # Patch nghttp2 pkg config file to support static builds.
-COPY libnghttp2-*.patch ${NGHTTP2_VERSION}/
+COPY patches/libnghttp2-*.patch ${NGHTTP2_VERSION}/
 RUN cd ${NGHTTP2_VERSION} && \
     for p in $(ls libnghttp2-*.patch); do patch -p1 < $p; done && \
     autoreconf -i && automake && autoconf
@@ -49,7 +49,7 @@ RUN curl -o ${CURL_VERSION}.tar.xz https://curl.se/download/${CURL_VERSION}.tar.
 RUN tar xf ${CURL_VERSION}.tar.xz
 
 # Patch Curl.
-COPY curl-*.patch ${CURL_VERSION}/
+COPY patches/curl-*.patch ${CURL_VERSION}/
 
 # Re-generate the configure script
 RUN cd ${CURL_VERSION} && \