link to another markdown file code example

Example 1: markdown link to section in another file

#  Main section

##  [sub-section](./child.md#sub-section)    
##  [sub-section](/child.md#sub-section)
##  [sub-section](child.md#sub-section)

Example 2: markdown link to file

[a link](./path/to/file.txt)
[a link](path%20with%20spaces/other_file.txt)