add tool description, feature list and usage instructions to README

README.md

@@ -1,5 +1,76 @@
 # mrvc (max room version checker)
 
+mrvc is a tool for determining how many members support which maximum room version for a given Matrix room.
+
+Its output looks something like this:
+
+```
+Room:
+  !amwlFMejXQcoCxNYHH:matrix.org -> 1131
+Given Aliases:
+  #element-x-ios:matrix.org
+Version Support:
+  unkown -> 103
+    ...
+    unknown -> 101
+      unknown -> 101
+  v10 -> 2
+    Synapse -> 2
+      1.76.0 -> 1
+      1.85.2 -> 1
+  v11 -> 87
+    Conduwuit -> 1
+      0.4.6 (8f7ade4) -> 1
+    Synapse -> 68
+      ...
+      1.134.0 -> 22
+      1.135.0+pro.4 -> 3
+      1.135.0 -> 17
+    Tuwunel -> 9
+      1.2.0 -> 1
+      1.3.0 -> 8
+    conduwuit -> 2
+      0.5.0 (3e57b7d) -> 1
+      0.5.0 (bec19df-dirty) -> 1
+    continuwuity -> 7
+      ...
+      0.5.0-rc.7 (583cb92) -> 1
+      0.5.0-rc.7 (e4a43b1) -> 1
+  v12 -> 939
+    Conduit -> 2
+      0.10.8 -> 2
+    Synapse -> 937
+      1.135.2 -> 34
+      1.136.0 -> 87
+      1.136.0 (b=HEAD,t=v1.136.0,e8c6cb3d9e) -> 1
+      1.136.0 (b=matrix-org-hotfixes-priv,a4db588e87) -> 815
+```
+
+## Features
+
+- Show member count broken down by maximum room version, Matrix server implementation and version and optionally homeserver name.
+- Check multiple rooms at once by setting the `--room` flag multiple times.
+
+## Usage
+
+Get a version of mrvc using either `go build` or nix.  
+Furthermore a Matrix account with its access token is required.
+One way to obtain the access token is by going into Element -> Settings -> "Help & About" and at the bottom under "Advanced" the access token can be copied.
+
+Then just run:
+
+```
+mrvc --user-id @myuser:myhomeserver.tld --token token --room '#name:homeserver.tld'
+```
+
+Note that each option is also available via an environment variable, which is especially useful for providing the access token to mrvc.
+
+For a list of all the available options run:
+
+```
+mrvc -h
+```
+
 ## License
 
 mrvc is licensed under the [MIT License](./License).