nvim: plugin: Add a plugin to help with epoch timestamp conversions

We look at logs frequently these days with epoch timestamps and this
helps with getting the human readable timestamp and vice versa.

nvim/.config/nvim/plugin/epoch-converter.vim

@@ -0,0 +1,14 @@
+function GetHumanReadableDate()
+  let epoch = expand("<cword>")
+  let date = trim(system("date -d @" . epoch))
+  echo date
+endfunction
+
+function GetEpochDate()
+  normal! `<v`>y
+  let date = trim(system("date -d " . trim(shellescape(@@)) . ' "+%s"'))
+  echo date
+endfunction
+
+nnoremap <LocalLeader>e :call GetHumanReadableDate()<CR>
+xnoremap <LocalLeader>e :call GetEpochDate()<CR>