fix: Typos and truncated code snippet in standard libraries blog (#31)

The truncated code snippet was due to the `inline-dafny` implementation
only understanding source files where the code is contained in an
explicit module, since it assumes any line that is literally "}\n" is
the end of a module and hence the terminator for the snippet. I indented
all of the manual snippets to align with the corrected one at the end.

Also corrected a couple of typos and included the sample input (thanks
@stefan-aws!)