Add readme

DESCRIPTION

@@ -1,5 +1,5 @@
 Package: ubigen
-Title: Graphical Interface for Finding Patterns in Gene Expression
+Title: Graphical Interface for Finding Ubiquitous Genes
 Version: 0.0.0.9000
 Authors@R:
     person(
@@ -11,7 +11,7 @@ Authors@R:
     )
 Description: This package contains precomputed data including comparisons in
     gene expression. It provides a graphical interface to analyze and visualize
-    those data.
+    those data to rank genes based on how ubiquitously expressed they are.
 License: AGPL (>= 3)
 Encoding: UTF-8
 Roxygen: list(markdown = TRUE)

README.md

@@ -0,0 +1,41 @@
+# Ubigen
+
+This R package contains precomputed data including comparisons in gene
+expression within the [GTEx database](https://gtexportal.org). It provides a
+graphical interface to analyze and visualize those data to rank genes based on
+how ubiquitously expressed they are.
+
+## Installation
+
+You can install the development version of `ubigen` using:
+
+```r
+# install.packages("remotes")
+remotes::install_git("https://code.johrpan.de/johrpan/ubigen.git")
+```
+
+## Usage
+
+You only need one function to get started. It will run the application and
+serve the graphical user interface which can be viewed using your preferred
+web browser.
+
+```r
+ubigen::run_app()
+```
+
+For additional information, take a look at the built-in documentation
+(`?ubigen::run_app`).
+
+## License
+
+This program is free software: you can redistribute it and/or modify it under
+the terms of the GNU Affero General Public License as published by the Free
+Software Foundation, either version 3 of the License, or (at your option) any
+later version.
+
+This program is distributed in the hope that it will be useful, but WITHOUT ANY
+WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A
+PARTICULAR PURPOSE. See the
+[GNU Affero General Public License}(https://www.gnu.org/licenses/agpl-3.0.html)
+for more details.