Improve manual in various ways (inputs, sort_by, foreach sections, etc.) (#2744)

- Add error/0 and mentions null input behavior (close #2231)
- Explain value iterator suffix syntax .foo[] (close #1047)
- Mention array slicing is also zero-based (close #2094)
- Add examples of input and inputs filters (close #2216, close #2470)
- Improve sort_by about multiple values (close #2103, close #2467, close #2474)
- Improve foreach section and simplify examples (close #1148, close #2169)
- Fix recurse/1 document on how it is identical using recurse/2 (close #2036, close #2412)
- Add non-string examples of index/1, rindex/1 (close #1422)
- Simplify the example of truncate_stream/1 (close #1736)

docs/content/download/default.yml

@@ -155,7 +155,7 @@ body:
       You can build it using the usual `./configure && make && sudo
       make install` rigmarole.
 
-      If you're interested in using the lastest development version, try:
+      If you're interested in using the latest development version, try:
 
           git clone --recursive https://github.com/jqlang/jq.git
           cd jq