feat: create seinebasin3 R package

.Rbuildignore

+^seinebasin3\.Rproj$
+^\.Rproj\.user$
+^data-raw$

.gitignore

+.Rproj.user

DESCRIPTION

+Package: seinebasin3
+Title: What the Package Does (One Line, Title Case)
+Version: 0.0.0.9000
+Authors@R: 
+    person("First", "Last", , "first.last@example.com", role = c("aut", "cre"))
+Description: What the package does (one paragraph).
+License: `use_mit_license()`, `use_gpl3_license()` or friends to pick a
+    license
+Encoding: UTF-8
+Roxygen: list(markdown = TRUE)
+RoxygenNote: 7.3.2
+Imports: 
+    openxlsx2

NAMESPACE

+# Generated by roxygen2: do not edit by hand
+

seinebasin3.Rproj

+Version: 1.0
+
+RestoreWorkspace: No
+SaveWorkspace: No
+AlwaysSaveHistory: Default
+
+EnableCodeIndexing: Yes
+Encoding: UTF-8
+
+AutoAppendNewline: Yes
+StripTrailingWhitespace: Yes
+LineEndingConversion: Posix
+
+BuildType: Package
+PackageUseDevtools: Yes
+PackageInstallArgs: --no-multiarch --with-keep.source
+PackageRoxygenize: rd,collate,namespace