CONTRIBUTING.md: Set increasing numbers on lists of items

It's easier to read it directly outside the markdown interpretation.

Author: fxlb

CONTRIBUTING.md

@@ -39,34 +39,34 @@ and ask!
 1) Check that there isn't a pull request already opened for the changes you
    intend to make.
 
-1) [Fork](https://help.github.com/articles/fork-a-repo/) the Tcpdump
+2) [Fork](https://help.github.com/articles/fork-a-repo/) the Tcpdump
    [repository](https://github.com/the-tcpdump-group/tcpdump).
 
-1) The easiest way to test your changes on multiple operating systems and
+3) The easiest way to test your changes on multiple operating systems and
    architectures is to let the upstream CI test your pull request (more on
    this below).
 
-1) Setup your git working copy
+4) Setup your git working copy
    ```
    git clone https://github.com/<username>/tcpdump.git
    cd tcpdump
    git remote add upstream https://github.com/the-tcpdump-group/tcpdump
    git fetch upstream
    ```
 
-1) Do a `touch .devel` in your working directory.
+5) Do a `touch .devel` in your working directory.
    Currently, the effect is
    * add (via `configure`, in `Makefile`) some warnings options (`-Wall`,
      `-Wmissing-prototypes`, `-Wstrict-prototypes`, ...) to the compiler if it
      supports these options,
    * have the `Makefile` support `make depend` and the `configure` script run it.
 
-1) Configure and build
+6) Configure and build
    ```
    ./configure && make -s && make check
    ```
 
-1) Add/update tests
+7) Add/update tests
    The `tests` directory contains regression tests of the dissection of captured
    packets.  Those captured packets were saved running tcpdump with option
    `-w sample.pcap`.  Additional options, such as `-n`, are used to create relevant
@@ -96,30 +96,30 @@ and ask!
    It is often useful to have test outputs with different verbosity levels
    (none, `-v`, `-vv`, `-vvv`, etc.) depending on the code.
 
-1) Test using `make check` (current build options) and `./build_matrix.sh`
+8) Test using `make check` (current build options) and `./build_matrix.sh`
    (a multitude of build options, build systems and compilers). If you can,
    test on more than one operating system. Don't send a pull request until
    all tests pass.
 
-1) Try to rebase your commits to keep the history simple.
+9) Try to rebase your commits to keep the history simple.
    ```
    git fetch upstream
    git rebase upstream/master
    ```
    (If the rebase fails and you cannot resolve, issue `git rebase --abort`
    and ask for help in the pull request comment.)
 
-1) Once 100% happy, put your work into your forked repository using `git push`.
+10) Once 100% happy, put your work into your forked repository using `git push`.
 
-1) [Initiate and send](https://help.github.com/articles/using-pull-requests/)
+11) [Initiate and send](https://help.github.com/articles/using-pull-requests/)
     a pull request.
     This will trigger the upstream repository CI tests.
 
 
 ## Code style and generic remarks
 1) A thorough reading of some other printers code is useful.
 
-1) To help learn how tcpdump works or to help debugging:
+2) To help learn how tcpdump works or to help debugging:
    You can configure and build tcpdump with the instrumentation of functions:
    ```
    $ ./configure --enable-instrument-functions
@@ -157,12 +157,12 @@ and ask!
 
    The library libbfd is used, therefore the binutils-dev package is required.
 
-1) Put the normative reference if any as comments (RFC, etc.).
+3) Put the normative reference if any as comments (RFC, etc.).
 
-1) Put the format of packets/headers/options as comments if there is no
+4) Put the format of packets/headers/options as comments if there is no
    published normative reference.
 
-1) The printer may receive incomplete packet in the buffer, truncated at any
+5) The printer may receive incomplete packet in the buffer, truncated at any
    random position, for example by capturing with `-s size` option.
    This means that an attempt to fetch packet data based on the expected
    format of the packet may run the risk of overrunning the buffer.
@@ -356,20 +356,20 @@ and ask!
    The `nd_*` type for a byte in a sequence of bytes is `nd_byte`; an
    *N*-byte sequence should be declared as `nd_byte[N]`.
 
-1) Do invalid packet checks in code: Think that your code can receive in input
+7) Do invalid packet checks in code: Think that your code can receive in input
    not only a valid packet but any arbitrary random sequence of octets (packet
    * built malformed originally by the sender or by a fuzz tester,
    * became corrupted in transit or for some other reason).
 
    Print with: `nd_print_invalid(ndo);	/* to print " (invalid)" */`
 
-1) Use `struct tok` for indexed strings and print them with
+8) Use `struct tok` for indexed strings and print them with
    `tok2str()` or `bittok2str()` (for flags).
    All `struct tok` must end with `{ 0, NULL }`.
 
-1) Avoid empty lines in output of printers.
+9) Avoid empty lines in output of printers.
 
-1) A commit message must have:
+10) A commit message must have:
    ```
    First line: Capitalized short summary in the imperative (50 chars or less)
 
@@ -381,14 +381,14 @@ and ask!
    the body.
    ```
 
-1) Avoid non-ASCII characters in code and commit messages.
+11) Avoid non-ASCII characters in code and commit messages.
 
-1) Use the style of the modified sources.
+12) Use the style of the modified sources.
 
-1) Don't mix declarations and code.
+13) Don't mix declarations and code.
 
-1) tcpdump requires a compiler that supports C99 or later, so C99
+14) tcpdump requires a compiler that supports C99 or later, so C99
    features may be used in code, but C11 or later features should not be
    used.
 
-1) Avoid trailing tabs/spaces
+15) Avoid trailing tabs/spaces