Add fastpolicytree link to README (#177)

Author: erikcs

.github/workflows/pages.yml

@@ -39,7 +39,7 @@ jobs:
           R CMD INSTALL .
 
           # Use pkgdown v1.5
-          sudo Rscript -e "install.packages(c('fs', 'highlight', 'httr', 'memoise', 'openssl', 'purrr', 'rmarkdown', 'rstudioapi', 'whisker', 'xml2', 'yaml'))"
+          sudo Rscript -e "install.packages(c('fs', 'highlight', 'httr', 'memoise', 'openssl', 'purrr', 'rmarkdown', 'rstudioapi', 'whisker', 'xml2', 'yaml', 'rematch2', 'fansi'))"
           sudo Rscript -e "install.packages('https://cran.r-project.org/src/contrib/Archive/pkgdown/pkgdown_1.5.1.tar.gz', repos = NULL, type = 'source')"
 
           # Build site

README.md

@@ -9,7 +9,7 @@ Some helpful links for getting started:
 
 * The [R package documentation](https://grf-labs.github.io/policytree/) contains usage examples and method references.
 * For community questions and answers around usage, see the GitHub [issues page](https://github.com/grf-labs/policytree/issues).
-* The package [sparse policytree](https://github.com/Yale-Medicaid/sparsepolicytree) uses an alternate solver that may be faster on large datasets with sparse categorical features.
+* The packages [fastpolicytree](https://CRAN.R-project.org/package=fastpolicytree) and [sparsepolicytree](https://github.com/beniaminogreen/sparsepolicytree) implement modified solvers that may offer improved performance on larger datasets.
 
 ### Installation