Add TOC for README.

Hello.

It seems that there is problem with importing Google types.

I'm using latest macos with protobuf installed via brew install protobuf
I've also tried on Ubuntu 18.04 copying includes folder to /usr/local/include/google/protobuf/
Results are the same.

git clone https://github.com/iamazeem/proto-convert.git
cd proto-convert/test
../bin/proto-convert -m j2b -p test.proto -t test.Message -i test.json -o test.bin
Possible 'import' issue! Use a single self-contianed .proto file! cannot load such file -- google/protobuf

ls -la  /usr/local/include/google/protobuf/
total 4072
drwxr-xr-x  71 krr  admin    2272 Jun  8 16:15 .
drwxr-xr-x   3 krr  admin      96 Jun  8 16:15 ..
-rw-r--r--   1 krr  admin    6365 Jun  8 16:15 any.h
-rw-r--r--   1 krr  admin   14209 Jun  8 16:15 any.pb.h
-rw-r--r--   1 krr  admin    5916 Jun  8 16:15 any.proto

I'm trying to convert my .proto file into binary format tp import converted binay file i6n postman to test with http put call. Over all to test .proto files with http call. But my main .proto files calling many .proto files to get messages? What should i change in the mentioned command? I'm raising it in issue, since i couldn't find other way to reach you?

I'm trying to use this with stdin but it is not working:

20220801T151952 [email protected]:~/sw/d/gitlab.com/aucampia/pvt/scratchpad/tech/cloudevents
$ proto-convert --mode j2b --proto spec/cloudevents.proto --msgtype io.cloudevents.v1.CloudEvent --verbose --input <(echo '{}') --output /dev/stdout
ERROR: Input file not found! [/dev/fd/63]
20220801T151957 [email protected]:~/sw/d/gitlab.com/aucampia/pvt/scratchpad/tech/cloudevents
$ echo '{}' | proto-convert --mode j2b --proto spec/cloudevents.proto --msgtype io.cloudevents.v1.CloudEvent --verbose --input /dev/stdin --output /dev/stdout
ERROR: Input file not found! [/dev/stdin]

If i try to convert to json using a proto file that contains import of the other proto file, this will bring error: proto file was not found or had errors..
To fix this, the protoc call must contain a special parameter --proto_path or -I with the path to search for other proto files..
This means, that this path, please, must be added to proto-convert as an additional parameter and used then in the internal protoc call..

Is proto-convert able to handle import in proto files?