Also changed event trigger for idf-extension to use config-updated, as this makes more logical sense
Includes functionality for defining local (single .rst file) substitution strings that depend on chip target.
Substitutions can be defined with {IDF_TARGET_X: default = "IO3", esp32 = "IO4"} and then used locally as {IDF_TARGET_X}
Also added global substitution for TRM links {IDF_TARGET_TRM_URL}
