Add README for usage and instructions

Author: zhouselena

.evergreen/perfcomp/README.md

@@ -0,0 +1,55 @@
+# perfcomp
+
+**perfcomp** is a performance analyzer on a PR commit basis.
+
+## 📦 Installation
+
+To install the latest version:
+
+```bash
+go install github.com/mongodb-labs/drivers-evergreen-tools/perfcomp
+```
+
+Or build it locally in `bin/perfcomp`:
+
+```bash
+bash build.sh
+```
+
+## 🔧 Usage
+
+To use `perfcomp`, you should have an analytics node URI env variable called `PERF_URI_PRIVATE_ENDPOINT`. You can request for it from the devprod performance team.
+
+To run in your project repository, you need to create a [performance context](https://performance-monitoring-and-analysis.server-tig.prod.corp.mongodb.com/contexts) that captures all benchmarks in your project. Feel free to refer to the [Go Driver context](https://performance-monitoring-and-analysis.server-tig.prod.corp.mongodb.com/context/name/GoDriver%20perf%20task) as a template. Then, add the context to the `projectToPerfContext` map in `./cmd/perfcomp/compare.go`.
+
+```bash
+perfcomp is a cli that reports stat-sig results between evergreen patches with the mainline commit
+
+Usage:
+  perfcomp [command]
+
+Available Commands:
+  compare     compare evergreen patch to mainline commit
+  mdreport    generates markdown output after run
+```
+
+### Commands
+
+#### compare
+```bash
+compare evergreen patch to mainline commit
+
+Usage:
+  perfcomp compare [version_id] [flags]
+
+Flags:
+  --project string   specify the name of an existing Evergreen project (default "mongo-go-driver")
+```
+
+#### mdreport
+```bash
+generates markdown output after compare run (must be run after `compare`)
+
+Usage:
+  perfcomp mdreport
+```