mentioned analog editing in tastudio

I spent years explaining this over and over and didn't ever feel like going ahead and documenting it. but bizhawk refuses to die and people keep asking, so let it be here

README.md

@@ -276,6 +276,21 @@ More disclaimers: Develop a habit to always flush saves manually every time you
 
 For now, the best way to learn how to TAS is to browse pages like [BasicTools](https://tasvideos.org/TasingGuide/BasicTools) on TASVideos and watch tutorials like [The8bitbeast's](https://www.youtube.com/playlist?list=PLlJzD6wWmoXmihK13itZJ-mzjK3SD1EaM) and [Sand_Knight and dwangoAC's](https://youtu.be/6tJniMaR2Ps).
 
+## TAStudio
+
+A lot of useful information is presented in [the video tutorials thread on TASVideos](https://tasvideos.org/Forum/Topics/21792).
+
+# Analog controls
+
+Enter analog editing mode by double-clicking on an analog input cell. The cell color will change. There are several ways to edit values:
+
+* Arrow keys (see the `TAStudio` section in the `Hotkeys` menu)
+* Numeric input
+* Mouse dragging
+* Using the `Virtual Pad` tool while the `Recording mode` is enabled in TAStudio
+
+While in analog editing mode, you can select multiple rows if you hold Shift or Control key and click on the `Frame#` column. That will allow you editing all those cells at once using Arrow keys or numeric input.
+
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 ### External tools