prebuilts: improve doc

Author: cirosantilli

README.adoc

@@ -226,9 +226,9 @@ After this, to start using Docker again will you need another:
 [[prebuilt]]
 ==== Getting started with prebuilts
 
-We don't currently provide a full prebuilt because it would be too big to host freely.
+We don't currently provide a full prebuilt because it would be too big to host freely, notably because of the cross toolchain.
 
-However, if you just want to quickly try out running our kernel modules, try this:
+However, we do provide a prebuilt filesystem and kernel, which allows you to quickly try out running our kernel modules:
 
 . Download QEMU and this repo:
 +
@@ -243,7 +243,7 @@ cd linux-kernel-module-cheat
 unzip images-*.zip
 ....
 +
-It is link:https://stackoverflow.com/questions/24987542/is-there-a-link-to-github-for-downloading-a-file-in-the-latest-release-of-a-repo/50540591#50540591[not possible to automate this step without the API], and I'm not venturing there this time
+It is link:https://stackoverflow.com/questions/24987542/is-there-a-link-to-github-for-downloading-a-file-in-the-latest-release-of-a-repo/50540591#50540591[not possible to automate this step without the API], and I'm not venturing there at this time, pull requests welcome.
 . checkout to the prebuilt repo version so that the scripts and documentation will be compatible with it, and run with the `-P` option:
 +
 ....