Upating Local install docs for people on a clean clone (#645)

Issue reported here: actualbudget/actual#4377

https://deploy-preview-645.www.actualbudget.org/docs/install/local

It turns out that yarn doesn't let you run scripts without first
installing dependencies, so users will have to type it in the install
manually.

The other alternative is to run the script with npm but that would add
confusion.

I think yarn workspace focus is the best option to pick but here was the
options:

- Instruct users to ```yarn install``` (which would install all deps) -
1.07GB
- Instruct users to ```yarn workspaces focus @actual-app/sync-server
--production``` (which is a long command) - 60.6MB
- Create a new shell script to run the command ```
./install-server.sh```

In future we might want to consider packaging the server up into an
executable. That way the user wont have to install node/deal with any of
this stuff.

Here's an example packager - i've never used it:
https://github.com/nexe/nexe

docs/actual-server-repo-move.md

@@ -35,7 +35,7 @@ The reasons for this change are as follows:
   ```
   3. Install the required dependencies for the server:
   ```
-  yarn install:server
+  yarn workspaces focus @actual-app/sync-server --production
   ```
   4. Run the server with:
   ```

docs/contributing/project-details/index.md

@@ -38,7 +38,7 @@ The shared underlying functionality component used by both the web/desktop front
 
 ## Sync Server
 
-The Sync Server, also known as Actual Server, holds all of the code for the synchronization element of the Actual Budget application. Actual server has a dependency of Actual so when you pull Actual Server and deploy it to your hosting method of choice, be that Fly, Local etc. and run `yarn install:server` Actual will be downloaded as a dependency from NPM and installed into the Actual Server deployment.
+The Sync Server, also known as Actual Server, holds all of the code for the synchronization element of the Actual Budget application. Actual server has a dependency of Actual so when you pull Actual Server and deploy it to your hosting method of choice, be that Fly, Local etc. and run `yarn workspaces focus @actual-app/sync-server --production` Actual will be downloaded as a dependency from NPM and installed into the Actual Server deployment.
 
 You can see this in the [package.json](https://github.com/actualbudget/actual/blob/master/packages/sync-server/package.json) file;
 

docs/install/local.md

@@ -29,7 +29,7 @@ Actual server is used for syncing changes across devices. It comes with the late
     ```
 3. Install all the required dependencies using yarn.
     ```bash
-    yarn install:server
+    yarn workspaces focus @actual-app/sync-server --production
     ```
 
 ## Running Actual
@@ -91,7 +91,7 @@ When accessing Actual for the first time, you may be prompted to provide a URL f
 
 1. Stop the server if it’s running. You can use the keyboard shortcut <kbd>CTRL-C</kbd> (even on macOS) to stop the server or close the terminal window it’s running from.
 2. Run `git pull` from the directory you cloned the project into. This will download the latest server code.
-3. Run `yarn install` from that same directory. This will download the latest web client code, along with any updated dependencies for the server.
+3. Run `yarn workspaces focus @actual-app/sync-server --production` from that directory. This will download the latest web client code, along with any updated dependencies for the server.
 4. Restart the server by running `yarn start`.
 
 Actual is constantly evolving to include new features and improve the user's experience. It is always recommended that your local installation be updated with our [latest releases](https://actualbudget.org/docs/releases).