Feature/Typing postMessageCommands

[DavidM42]

• also some linting things

fixes #30

[NiklasMerz]

Error see build:

ERROR in pecuniator-api/main.ts:29:29 - error TS1109: Expression expected.

29             if (data.result?.transactions?.length > 0) {
                               ~
pecuniator-api/main.ts:29:43 - error TS1109: Expression expected.

29             if (data.result?.transactions?.length > 0) {
                                             ~
pecuniator-api/main.ts:29:54 - error TS1005: ':' expected.

29             if (data.result?.transactions?.length > 0) {
                                                        ~

[DavidM42]

You sure this is a result of my changes? I do not remember editing these lines