docs: first describe simple read and write without streaming (#49834)

Author: fonsp

doc/src/manual/networking-and-streams.md

@@ -120,7 +120,28 @@ of common properties.
 
 ## Working with Files
 
-Like many other environments, Julia has an [`open`](@ref) function, which takes a filename and
+You can write content to a file with the `write(filename::String, content)` method:
+
+```julia-repl
+julia> write("hello.txt", "Hello, World!")
+13
+```
+
+_(`13` is the number of bytes written.)_
+
+You can read the contents of a file with the `read(filename::String)` method, or `read(filename::String, String)`
+to the contents as a string:
+
+```julia-repl
+julia> read("hello.txt", String)
+"Hello, World!"
+```
+
+
+### Advanced: streaming files
+
+The `read` and `write` methods above allow you to read and write file contents. Like many other
+environments, Julia also has an [`open`](@ref) function, which takes a filename and
 returns an [`IOStream`](@ref) object that you can use to read and write things from the file. For example,
 if we have a file, `hello.txt`, whose contents are `Hello, World!`: