Update docs

Author: jakobnissen

docs/src/files.md

@@ -133,12 +133,18 @@ FASTAReader(GzipDecompressorStream(open("seqs.fna.gz"; lock=false)))
 To use rdr `rdr` and `wtr` macros with `do`-syntax, use the `defer` function.
 The only purpose of the defer function is to enable `do`-syntax:
 
-```julia
-record = FASTARecord("my_header", "TAGAG")
+```jldoctest
+julia> using CodecZlib # for gzip files
 
-defer(wtr"seqs.fna.gz") do writer
-    write(writer, record)
-end
+julia> defer(rdr"../test/data/test.fasta") do reader
+           println(identifier(first(reader)))
+       end
+abc
+
+julia> defer(wtr"seqs.fna.gz") do writer 
+           write(writer, FASTARecord("my_header", "TAGAG"))
+       end
+17
 ```
 
 ### Validate files

docs/src/index.md

@@ -79,14 +79,16 @@ For added convenience, you can also use the reader and writer macros `rdr""` and
 These macros use the file extensions to determine the biological sequence reader or writer type, and any file compresion.
 To use these macros with the `do`-syntax, you can use the `defer` function. Hence, the above code block can also be written in the following equivalent way:
 
-```julia
-using CodecZlib
+```jldoctest
+julia> using CodecZlib
 
-defer(rdr"seqs.fna.gz") do reader
-    for record in reader
-        println(identifier(record))
-    end
-end
+julia> defer(rdr"../test/data/seqs.fna.gz") do reader
+           for record in reader
+               println(identifier(record))
+           end
+       end
+seqa
+seqb
 ```
 
 ### Construct FASTA or FASTQ records from raw parts