List pyschrolib contributors in a separate file

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Author: Hongyuan Jia

src/r/DESCRIPTION

@@ -5,10 +5,9 @@ Version: 2.4.0
 Authors@R: c(
       person("Hongyuan", "Jia", email = "hongyuan.jia@bears-berkeley.sg", role = c("aut", "cre"), comment = c(ORCID = "0000-0002-0075-8183")),
       person(family = "The PsychroLib Contributors", role = c("ctb", "cph"),
-             email = "hongyuan.jia@bears-berkeley.sg",
-             comment = "Authors listed at https://github.com/psychrometrics/psychrolib/graphs/contributors"),
+             comment = "Authors listed in inst/PSYCHROLIB_AUTHORS.txt"),
       person(family = "ASHRAE", role = c("cph"),
-             comment = "Copyright 2017 ASHRAE Handbook  Fundamentals (https://www.ashrae.org) for equations and coefficients published ASHRAE Handbook  Fundamentals Chapter 1."))
+             comment = "Copyright 2017 ASHRAE Handbook Fundamentals (https://www.ashrae.org) for equations and coefficients published ASHRAE Handbook Fundamentals Chapter 1."))
 Maintainer: Hongyuan Jia <hongyuan.jia@bears-berkeley.sg>
 Description:
     'PsychroLib' <https://github.com/psychrometrics/psychrolib> is a library of

src/r/inst/PSYCHROLIB_AUTHORS.txt

@@ -0,0 +1,7 @@
+Authors ordered by first contribution
+
+Didier Thevenard
+David Meyer
+Daniel Gosnell
+Michael Lass <michael.lass@upb.de>
+Hongyuan Jia <hongyuan.jia@bears-berkeley.sg>