chore: bump to v0.2.1

fix: separate stylesheet of web app (#48) @bruceyyu 

refactor: Make duckdb optional (#47) @EydlinIlya 

fix: build path of react app @EydlinIlya 

fix: serialize NA values to null, not to charactrer "NA" (#43) @EydlinIlya

Author: bruceyyu

DESCRIPTION

@@ -1,6 +1,6 @@
 Package: GWalkR
 Title: Interactive Exploratory Data Analysis Tool
-Version: 0.2.0
+Version: 0.2.1
 Authors@R: c(
     person("Yue", "Yu", , "[email protected]", role = c("aut", "cre"),
            comment = c(ORCID = "0000-0002-9302-0793")),