Switch from Travis to Github action for connector repos

[agnes512]

To keep track of the status of all connector repos.

• loopback-connector-mongodb

• loopback-connector-mysql [WIP ci: switch from travis to github actions loopback-connector-mysql#439]

• loopback-connector-cassandra

• loopback-connector-postgresql [WIP Switch Travis to GitHub Actions loopback-connector-postgresql#473]

• loopback-connector-kv-redis

• loopback-connector

• loopback-connector-soap

• loopback-connector-rest

• loopback-connector-swagger -> this repo hasn't been updated for 1.5 years 👀 . Deprecated.

• loopback-component-storage -> only for LB3. Reached EOL.

• loopback-connector-jsonrpc

• loopback-connector-openapi

[agnes512]

loopbackio/loopback-connector-mongodb#613

[dhmlau]

Thanks @agnes512. I believe the loopback-connector-swagger has deprecated. loopback-connector-openapi should be used. So i think it's safe not to switch to GitHub Actions.
@raymondfeng, thoughts?

[dhmlau]

Also loopback-component-storage reached end of life, so there's no need to move to GH Actions.

[bajtos]

AFAICT, loopback-connector-openapi does not require any special setup, it's just npm install and npm test. The transition from Travis to GitHub action should be pretty trivial.

See loopback-connector-openapi/.travis.yml:

language: node_js
node_js:
 - 10
 - 12
 - 14

(It would be great to remove Node.js 10 and add Node.js 15 to the build matrix after the migration is done.)