Retrieve and build protobuf from remote URLs (#158)

Currently, Freyja is using cargo git dependencies to reference the proto packages from other ESDV projects such as Ibeji. This has caused compatibility issues and needs to be updated. This PR makes a change to pull the content from a remote URL and build the proto files within the Freyja repo. Inspired by UProtocol: https://github.com/eclipse-uprotocol/up-rust/blob/main/build.rs

Also makes a minor update to the install instructions in the README, which required updating the markdown-ci workflow due to a recent regression in the tool that it uses (see tcort/markdown-link-check#304)

Fixes #157

.accepted_words.txt

@@ -33,6 +33,7 @@ ci
 cli
 CloudAdapter
 CloudConnector
+cmake
 com
 CONFIG
 config
@@ -72,6 +73,7 @@ Freyja
 Freyja's
 freyja
 Freyr
+gcc
 genpkey
 github
 githubusercontent

.github/workflows/markdown-ci.yml

@@ -27,5 +27,5 @@ jobs:
     steps:
     - uses: actions/checkout@v2
     - run: |
-        npm install markdown-link-check
+        npm install markdown-link-check@3.11.2
         find . -type d \( -name node_modules -o -name .github \) -prune -o -type f -name '*.md' -print0 | xargs -0 -n1 node_modules/.bin/markdown-link-check --config ./tools/.markdownlinkcheck.json --quiet