docs: add chart to manual

MANUAL

@@ -77,6 +77,7 @@ account name or transaction description.  Here are some commands to try
  hledger histogram                     # transactions per day, or other interval
  hledger ui                            # curses ui, if installed with -fvty
  hledger web                           # web ui, if installed with -fweb
+ hledger chart                         # make a balance chart, if installed with -fchart
  hledger -f new.ledger add             # record transactions from the command line
 
 Reference
@@ -113,6 +114,7 @@ Here is the command-line help::
    stats     - show various statistics for a ledger
    ui        - run a simple text-based UI
    web       - run a simple web-based UI
+   chart     - generate a balances pie chart
    test      - run self-tests
  
  PATTERNS are regular expressions which filter by account name.
@@ -123,6 +125,7 @@ Here is the command-line help::
  
  Options:
   -f FILE  --file=FILE          use a different ledger/timelog file; - means stdin
+           --no-new-accounts    don't allow to create new accounts
   -b DATE  --begin=DATE         report on transactions on or after this date
   -e DATE  --end=DATE           report on transactions before this date
   -p EXPR  --period=EXPR        report on transactions during the specified period
@@ -147,6 +150,8 @@ Here is the command-line help::
            --binary-filename    show the download filename for this hledger build
            --debug              show extra debug output; implies verbose
            --debug-no-ui        run ui commands with no output
+  -o FILE  --output=FILE        chart: output filename (default: hledger.png)
+           --size=WIDTHxHEIGHT  chart: image size (default: 1024x1024)
  
 File format
 ...........
@@ -225,6 +230,13 @@ balance
 
 The balance command displays accounts and their balances.
 
+chart
+'''''
+
+The chart command generates a pie chart image for your account balances.
+The image will have filename "hledger.png" (or use -o/--output) and
+dimensions 1024x1024 (or use --size=WIDTHxHEIGHT).
+
 histogram
 '''''''''