Update Alpine Section of the README

- Update the note regarding Alpine versions supporting which NodeJS versions

Author: luni-moon

README.md

@@ -800,7 +800,7 @@ curl -o- https://raw.githubusercontent.com/nvm-sh/nvm/v0.39.1/install.sh | bash
 apk add -U curl bash ca-certificates openssl ncurses coreutils python2 make gcc g++ libgcc linux-headers grep util-linux binutils findutils
 curl -o- https://raw.githubusercontent.com/nvm-sh/nvm/v0.39.1/install.sh | bash
 ```
-_Note: Alpine Linux 3.5 - 3.12 may install older versions of NodeJS. For the best results, please use Alpine Linux 3.13+._
+_Note: Alpine Linux 3.5 - 3.12 may install older versions of NodeJS, since these versions don't support the LTS version(s) of NodeJS, which require the package `python3` to successfully build, whereas Alpine 3.13+ does support it. For the best results, please use Alpine Linux 3.13+._
 
 The Node project has some desire but no concrete plans (due to the overheads of building, testing and support) to offer Alpine-compatible binaries.